Liquid crystal display device

ABSTRACT

A liquid crystal display device of the present invention includes in the following order from a viewing surface side a first polarizer, a first positive A plate having an in-plane retardation of 120 nm or greater and 155 nm or smaller, a positive C plate having a thickness retardation of 80 nm or greater and 100 nm or smaller, a first substrate, a second positive A plate having an in-plane retardation of 120 nm or greater and 155 nm or smaller, a horizontally aligned liquid crystal layer, a second substrate, a viewing angle compensation layer, and a second polarizer. The device further includes between the first polarizer and the first positive A plate a positive C plate having a thickness retardation of 30 nm or greater and 80 nm or smaller.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional application of U.S. patentapplication Ser. No. 16/584,519 filed on Sep. 26, 2019, which claimspriority under 35 U.S.C. § 119 to U.S. Provisional Application No.62/739,114 filed on Sep. 28, 2018, the contents of which areincorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to liquid crystal display devices. Thepresent invention specifically relates to a liquid crystal displaydevice including a horizontally aligned liquid crystal layer.

Description of Related Art

Liquid crystal display devices use a liquid crystal composition fordisplay. According to a typical display mode, voltage is applied to aliquid crystal composition sealed between a pair of substrates to changethe alignment of liquid crystal molecules in the liquid crystalcomposition according to the applied voltage, whereby the amount oflight transmitted is controlled. Such liquid crystal display deviceshave advantageous features such as thin profile, lightweight, and lowpower consumption, and are thus used in a wide range of fields.

As a technique related to liquid crystal display devices, JP 2009-251443A discloses a liquid crystal display device including a laminatedoptical film that includes a polarizer; a first optical compensationlayer which has a refractive index ellipsoid showing a relationship ofnx>ny>nz; and a second optical compensation layer which has a refractiveindex ellipsoid showing a relationship of nz>nx>ny, wherein thepolarizer and the first optical compensation layer are placed so that anabsorption axis of the polarizer is parallel to or perpendicular to aslow axis of the first optical compensation layer, and the polarizer andthe second optical compensation layer are placed so that an absorptionaxis of the polarizer is parallel to or perpendicular to a slow axis ofthe second optical compensation layer.

JP 2009-251442 A discloses a liquid crystal display device including alaminated optical film that includes a polarizer; a first opticalcompensation layer which has a refractive index ellipsoid showing arelationship of nx>ny=nz; and a second optical compensation layer whichhas a refractive index ellipsoid showing a relationship of nz>nx>ny,wherein the polarizer and the first optical compensation layer areplaced so that an absorption axis of the polarizer is parallel to orperpendicular to a slow axis of the first optical compensation layer,and the polarizer and the second optical compensation layer are placedso that an absorption axis of the polarizer is parallel to orperpendicular to a slow axis of the second optical compensation layer.

JP 2009-192611 A discloses a liquid crystal display device including alaminated optical film that includes a polarizer; a first opticalcompensation layer which has a refractive index ellipsoid showing arelationship of nz nx>ny; and a second optical compensation layer whichhas a refractive index ellipsoid showing a relationship of nx=ny>nz inthe stated order, wherein the polarizer and the first opticalcompensation layer are placed so that an absorption axis of thepolarizer is parallel to a slow axis of the first optical compensationlayer.

BRIEF SUMMARY OF THE INVENTION

A horizontal alignment mode, which controls the alignment of liquidcrystal molecules by rotating the liquid crystal molecules mainly in aplane parallel to the substrate surface, is drawing attention as adisplay mode of liquid crystal display devices because it can easilyprovide wide viewing angle characteristics. For example, many recentliquid crystal display devices such as smartphones and tablet personalcomputers use a horizontal alignment mode such as an in-plane switching(IPS) mode or a fringe field switching (FFS) mode.

Such a horizontal alignment mode liquid crystal display device includes,in the following order from the viewing surface side, a first polarizer,a first substrate provided with a color filter (CF) layer, ahorizontally aligned liquid crystal layer (hereinafter, also simplyreferred to as a liquid crystal layer), pixel electrodes, a secondsubstrate provided with a common electrode and thin film transistors(TFTs), and a second polarizer.

In order to reduce reflection of external light, the horizontalalignment mode liquid crystal display device may further include betweenthe first polarizer and the first substrate an out-cell retardationlayer including a positive A plate and a positive C plate, which areboth λ/4 plates, thereby providing a circularly polarizing plateconsisting of the first polarizer and the out-cell retardation layer.The horizontal alignment mode liquid crystal display deviceunfortunately fails to switch between on and off when circularlypolarized light is incident on the liquid crystal layer. Accordingly, anin-cell retardation layer that is a λ/4 plate needs to be disposed onthe liquid crystal layer side of the first substrate to convert thecircularly polarized light into linearly polarized light again beforebeing incident on the liquid crystal layer. In order to achieve thisstructure, the in-cell retardation layer and the out-cell retardationlayer need to be arranged with their slow axes perpendicular to eachother to cancel out the each other's retardations.

The in-cell retardation layer is, for example, a positive A plate whosethree principal refractive indices nx, ny, and nz satisfy the relation:nx>ny=nz. The positive A plate is preferably a film obtained by curingpolymerizable liquid crystal with ultraviolet (UV) rays because such afilm can be a thin film. In the above formula, “nx” represents therefractive index in the direction at which the in-plane refractive indexis maximum (i.e., slow axis direction), “ny” represents the refractiveindex in the direction perpendicular to the slow axis in a plane, and“nz” represents the refractive index in the thickness direction. Therefractive indices herein each indicate the value to light with awavelength of 550 nm at 23° C., unless otherwise stated.

In order to cancel the retardation of the in-cell retardation layer thatis a positive A plate, a negative A plate, whose three principalrefractive indices nx, ny, and nz satisfy the relation nx=nz>ny, ispreferred to be used as the out-cell retardation layer. The negative Aplate can cancel the retardation of the positive A plate at all theazimuths.

Unfortunately, materials for the negative A plate tend to be torn, i.e.,are fragile. In order to overcome this fragileness, the presentinventors used as an out-cell retardation layer a laminate including apositive C plate, whose three principal refractive indices nx, ny, andnz satisfy the relation: nx=ny<nz, and a positive A plate, so that theout-cell retardation layer worked as a negative A plate in appearance.

Differently from the negative A plate, the laminate including a positiveA plate and a positive C plate unfortunately fails to completely cancelthe retardation of the in-cell retardation layer that is a positive Aplate at almost all the azimuths. This incompleteness causes lightleakage when viewed from oblique directions in the black display stateto reduce the contrast ratio (CR) viewing angle in the black displaystate in a horizontally aligned liquid crystal display device includingthe in-cell retardation layer that is a positive A plate and theout-cell retardation layer that is a laminate including a positive Aplate and a positive C plate. The following gives specific descriptionof this with reference to simulation results.

FIG. 35 is a schematic cross-sectional view of a liquid crystal displaydevice of Comparative Embodiment 1. FIG. 36 is a schematiccross-sectional view of a liquid crystal display device of ComparativeEmbodiment 2.

As shown in FIG. 35, a liquid crystal display device 1R of ComparativeEmbodiment 1 includes, in the following order from the viewing surfaceside, a first polarizer 1P, a viewing angle compensation layer 30, afirst substrate including a CF layer (not shown), a horizontally alignedliquid crystal layer 1L, pixel electrodes, a second substrate includinga common electrode and TFTs (not shown), and a second polarizer 2P. Theviewing angle compensation layer 30 is a first laminate 31 including, inthe following order from the first polarizer 1P side, a positive A plate31A and a positive C plate 31C. The liquid crystal display device 1R ofComparative Embodiment 1 is a horizontal alignment mode liquid crystaldisplay device including the viewing angle compensation layer 30. In theschematic cross-sectional views, the “+A-Plate” means a positive Aplate, the “+C-Plate” means a positive C plate, the “FFS-LC” means a FFSmode liquid crystal layer that is a horizontally aligned liquid crystallayer, the angles of the first and second polarizers indicate theazimuth angles of their absorption axes, the angle of the liquid crystallayer indicates the alignment azimuth (slow axis) of liquid crystalmolecules in the black display state, and the angles of the other layersindicate the azimuth angles of their slow axes.

As shown in FIG. 36, a liquid crystal display device 1R of ComparativeEmbodiment 2 has the same structure as the liquid crystal display device1R of Comparative Embodiment 1 except that the device includes anout-cell retardation layer 21 between the viewing angle compensationlayer 30 and the first substrate and an in-cell retardation layer 22between the first substrate and the horizontally aligned liquid crystallayer 1L. The out-cell retardation layer 21 is a laminate including, inthe following order from the first polarizer 1P side, a first positive Aplate 1A and a positive C plate 1C. The in-cell retardation layer 22 isa second positive A plate 2A.

In each of Comparative Embodiments 1 and 2, the second substrate in theliquid crystal display device 1R has pixel electrodes with slits on thecommon electrode that has a sheet shape. In Comparative Embodiments 1and 2, the liquid crystal display device 1R generates a fringe electricfield between the pixel electrodes and the common electrode with voltageapplied, whereby liquid crystal molecules in the liquid crystal layer 1Lrotate. The voltage applied between the pixel electrodes and the commonelectrode is controlled to change the retardation of the liquid crystallayer 1L, whereby light is controlled to be transmitted or not. InComparative Embodiments 1 and 2, the liquid crystal display device 1R isa FFS mode liquid crystal display device.

In each of the liquid crystal display device 1R of ComparativeEmbodiment 1 and the liquid crystal display device 1R of ComparativeEmbodiment 2, the transmittance viewing angle in the black display statewith light having a wavelength of 550 nm was simulated at all theazimuths within the range of the polar angle of 0° to 80°, using aLCD-Master available from Shintec Co., Ltd.

FIG. 37 is a simulation result of the transmittance viewing angle in theblack display state of the liquid crystal display device of ComparativeEmbodiment 1. FIG. 38 is a simulation result of the transmittanceviewing angle in the black display state of the liquid crystal displaydevice of Comparative Embodiment 2. FIG. 37 and FIG. 38 show that lightleakage when viewed from oblique directions in the black display stateis more observed and the CR viewing angle in the black display state issmaller in the liquid crystal display device 1R of ComparativeEmbodiment 2, which includes the out-cell retardation layer 21 and thein-cell retardation layer 22, than in the liquid crystal display device1R of Comparative Embodiment 1, which does not include the out-cellretardation layer 21 and the in-cell retardation layer 22. In otherwords, differently from a negative A plate, the out-cell retardationlayer 21 that is a laminate including a positive A plate and a positiveC plate fails to completely cancel the retardation of the in-cellretardation layer 22 that is a positive A plate at all the azimuths.This incompleteness causes light leakage when viewed from obliquedirections in the black display state to reduce the CR viewing angle inthe black display state in a horizontally aligned liquid crystal displaydevice that includes the in-cell retardation layer that is a positive Aplate and the out-cell retardation layer that is a laminate including apositive A plate and a positive C plate.

JP 2009-251443 A, JP 2009-251442 A, and JP 2009-A disclose techniquesrelated to liquid crystal display devices including a vertically alignedliquid crystal layer but fail to disclose techniques related to liquidcrystal display devices including a horizontally aligned liquid crystallayer. The present inventors studied a case where the vertically alignedliquid crystal layer in the liquid crystal display device of JP2009-251443 A, JP 2009-251442 A, or JP 2009-192611 A was replaced by ahorizontally aligned liquid crystal layer. When the vertically alignedliquid crystal layer in JP 2009-251443 A, JP 2009-251442 A, or JP2009-192611 A is replaced by a horizontally aligned liquid crystallayer, positive A plates are disposed to sandwich the horizontallyaligned liquid crystal layer and circularly polarized light is incidenton the horizontally aligned liquid crystal layer. Such a display devicecannot switch between on and off even when circularly polarized light isincident on the horizontally aligned liquid crystal layer. The studythus revealed that the liquid crystal display device, in which thevertically aligned liquid crystal layer in JP 2009-251443 A, JP2009-251442 A, or JP 2009-192611 A is replaced by a horizontally alignedliquid crystal layer, cannot provide monochrome display.

The present invention has been made under the current situation in theart and aims to provide a liquid crystal display device capable ofreducing reflection of external light and suppressing light leakage whenviewed from oblique directions in the black display state.

(1) Another embodiment of the present invention is a liquid crystaldisplay device including in the following order from a viewing surfaceside: a first polarizer; a first positive A plate having an in-planeretardation of 120 nm or greater and 155 nm or smaller; a positive Cplate having a thickness retardation of 80 nm or greater and 100 nm orsmaller; a first substrate; a second positive A plate having an in-planeretardation of 120 nm or greater and 155 nm or smaller; a horizontallyaligned liquid crystal layer; a second substrate; a viewing anglecompensation layer; and a second polarizer, the liquid crystal displaydevice further including between the first polarizer and the firstpositive A plate a positive C plate having a thickness retardation of 30nm or greater and 80 nm or smaller.(2) In an embodiment of the present invention, the liquid crystaldisplay device includes the structure (1), and the viewing anglecompensation layer is a laminate including in the following order from asecond polarizer side a positive A plate having an in-plane retardationof 130 nm or greater and 150 nm or smaller and a positive C plate havinga thickness retardation of 80 nm or greater and 100 nm or smaller.(3) In an embodiment of the present invention, the liquid crystaldisplay device includes the structure (1), and the viewing anglecompensation layer is a laminate including in the following order from asecond polarizer side a biaxial retardation layer having an in-planeretardation of 80 nm or greater and 100 nm or smaller and an NZcoefficient of 1.3 or greater and 1.5 or smaller and a biaxialretardation layer having an in-plane retardation of 50 nm or greater and70 nm or smaller and an NZ coefficient of −1.2 or greater and −0.8 orsmaller.(4) In an embodiment of the present invention, the liquid crystaldisplay device includes the structure (1), and the viewing anglecompensation layer is a laminate including in the following order from asecond polarizer side a biaxial retardation layer having an in-planeretardation of 100 nm or greater and 130 nm or smaller and an NZcoefficient of 1.1 or greater and 1.3 or smaller and a biaxialretardation layer having an in-plane retardation of 10 nm or greater and30 nm or smaller and an NZ coefficient of −4.5 or greater and −3.5 orsmaller.(5) In an embodiment of the present invention, the liquid crystaldisplay device includes the structure (1), and the viewing anglecompensation layer is a λ/2 plate having an in-plane retardation of 230nm or greater and 320 nm or smaller and an NZ coefficient of 0.4 orgreater and 0.6 or smaller.(6) Another embodiment of the present invention is a liquid crystaldisplay device including in the following order from a viewing surfaceside: a first polarizer; a viewing angle compensation layer; a firstpositive A plate having an in-plane retardation of 120 nm or greater and155 nm or smaller; a positive C plate having a thickness retardation of80 nm or greater and 100 nm or smaller; a first substrate; a secondpositive A plate having an in-plane retardation of 120 nm or greater and155 nm or smaller; a horizontally aligned liquid crystal layer; a secondsubstrate; and a second polarizer, the liquid crystal display devicefurther including between the viewing angle compensation layer and thefirst positive A plate a positive C plate having a thickness retardationof 30 nm or greater and 80 nm or smaller.(7) In an embodiment of the present invention, the liquid crystaldisplay device includes the structure (6), and the viewing anglecompensation layer is a laminate including from a first polarizer side apositive A plate having an in-plane retardation of 130 nm or greater and150 nm or smaller and a positive C plate having a thickness retardationof 80 nm or greater and 100 nm or smaller.(8) In an embodiment of the present invention, the liquid crystaldisplay device includes the structure (6), and the viewing anglecompensation layer is a laminate including from a first polarizer side abiaxial retardation layer having an in-plane retardation of 80 nm orgreater and 100 nm or smaller and an NZ coefficient of 1.3 or greaterand 1.5 or smaller and a biaxial retardation layer having an in-planeretardation of 50 nm or greater and 70 nm or smaller and an NZcoefficient of −1.2 or greater and −0.8 or smaller.(9) In an embodiment of the present invention, the liquid crystaldisplay device includes the structure (6), and the viewing anglecompensation layer is a laminate including from a first polarizer side abiaxial retardation layer having an in-plane retardation of 100 nm orgreater and 130 nm or smaller and an NZ coefficient of 1.1 or greaterand 1.3 or smaller and a biaxial retardation layer having an in-planeretardation of 10 nm or greater and 30 nm or smaller and an NZcoefficient of −4.5 or greater and −3.5 or smaller.(10) In an embodiment of the present invention, the liquid crystaldisplay device includes the structure (6), and the viewing anglecompensation layer is a λ/2 plate having an in-plane retardation of 230nm or greater and 320 nm or smaller and an NZ coefficient of 0.4 orgreater and 0.6 or smaller.(11) Another embodiment of the present invention is a liquid crystaldisplay device including in the following order from a viewing surfaceside: a first polarizer; a viewing angle compensation layer; a firstpositive A plate having an in-plane retardation of 120 nm or greater and155 nm or smaller; a positive C plate having a thickness retardation of80 nm or greater and 100 nm or smaller; a first substrate; a secondpositive A plate having an in-plane retardation of 120 nm or greater and155 nm or smaller; a horizontally aligned liquid crystal layer; a secondsubstrate; and a second polarizer, the viewing angle compensation layerbeing a biaxial retardation layer having an in-plane retardation of 100nm or greater and 130 nm or smaller and an NZ coefficient of 1.1 orgreater and 1.3 or smaller, the liquid crystal display device furtherincluding between the viewing angle compensation layer and the firstpositive A plate a biaxial retardation layer having an in-planeretardation of 10 nm or greater and 30 nm or smaller and an NZcoefficient of −7.5 or greater and −6.5 or smaller.(12) Another embodiment of the present invention is a liquid crystaldisplay device including in the following order from a viewing surfaceside: a first polarizer; a viewing angle compensation layer; a firstpositive A plate having an in-plane retardation of 120 nm or greater and155 nm or smaller; a positive C plate having a thickness retardation of80 nm or greater and 100 nm or smaller; a first substrate; a secondpositive A plate having an in-plane retardation of 120 nm or greater and155 nm or smaller; a horizontally aligned liquid crystal layer; a secondsubstrate; and a second polarizer, the viewing angle compensation layerbeing a positive A plate having an in-plane retardation of 130 nm orgreater and 150 nm or smaller, the liquid crystal display device furtherincluding between the viewing angle compensation layer and the firstpositive A plate a positive C plate having a thickness retardation of130 nm or greater and 160 nm or smaller.(13) Another embodiment of the present invention is a liquid crystaldisplay device including in the following order from a viewing surfaceside: a first polarizer; a viewing angle compensation layer; a firstpositive A plate having an in-plane retardation of 120 nm or greater and155 nm or smaller; a positive C plate having a thickness retardation of80 nm or greater and 100 nm or smaller; a first substrate; a secondpositive A plate having an in-plane retardation of 120 nm or greater and155 nm or smaller; a horizontally aligned liquid crystal layer; a secondsubstrate; and a second polarizer, the viewing angle compensation layerbeing a biaxial retardation layer having an in-plane retardation of 80nm or greater and 100 nm or smaller and an NZ coefficient of 1.3 orgreater and 1.5 or smaller, the liquid crystal display device furtherincluding between the viewing angle compensation layer and the firstpositive A plate a biaxial retardation layer having an in-planeretardation of 50 nm or greater and 70 nm or smaller and an NZcoefficient of −2.0 or greater and −1.6 or smaller.

The present invention can provide a liquid crystal display devicecapable of reducing reflection of external light and suppressing lightleakage when viewed from oblique directions in the black display state.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a figure for illustrating the definitions of a polar angle andan azimuth angle in a liquid crystal display device.

FIG. 2 is a schematic cross-sectional view of a liquid crystal displaydevice of Embodiment 1.

FIG. 3 is a schematic cross-sectional view of a liquid crystal displaydevice of Embodiment 1-1.

FIG. 4 is a schematic cross-sectional view of a liquid crystal displaydevice of Embodiment 1-2.

FIG. 5 is a schematic cross-sectional view of a liquid crystal displaydevice of Embodiment 1-3.

FIG. 6 is a schematic cross-sectional view of a liquid crystal displaydevice of Embodiment 1-4.

FIG. 7 is a schematic cross-sectional view of a liquid crystal displaydevice of Embodiment 2.

FIG. 8 is a schematic cross-sectional view of a liquid crystal displaydevice of Embodiment 2-1.

FIG. 9 is a schematic cross-sectional view of a liquid crystal displaydevice of Embodiment 2-2.

FIG. 10 is a schematic cross-sectional view of a liquid crystal displaydevice of Embodiment 2-3.

FIG. 11 is a schematic cross-sectional view of a liquid crystal displaydevice of Embodiment 2-4.

FIG. 12 is a schematic cross-sectional view of a liquid crystal displaydevice of Embodiment 3.

FIG. 13 is a schematic cross-sectional view of a liquid crystal displaydevice of Embodiment 4.

FIG. 14 is a schematic cross-sectional view of a liquid crystal displaydevice of Embodiment 5.

FIG. 15 is a schematic cross-sectional view of a liquid crystal displaydevice of Example 1.

FIG. 16 is a simulation result of the transmittance viewing angle in theblack display state of the liquid crystal display device of Example 1.

FIG. 17 is a schematic cross-sectional view of a liquid crystal displaydevice of Example 2.

FIG. 18 is a simulation result of the transmittance viewing angle in theblack display state of the liquid crystal display device of Example 2.

FIG. 19 is a schematic cross-sectional view of a liquid crystal displaydevice of Example 3.

FIG. 20 is a simulation result of the transmittance viewing angle in theblack display state of the liquid crystal display device of Example 3.

FIG. 21 is a schematic cross-sectional view of a liquid crystal displaydevice of Example 4.

FIG. 22 is a simulation result of the transmittance viewing angle in theblack display state of the liquid crystal display device of Example 4.

FIG. 23 is a schematic cross-sectional view of a liquid crystal displaydevice of Example 5.

FIG. 24 is a simulation result of the transmittance viewing angle in theblack display state of the liquid crystal display device of Example 5.

FIG. 25 is a schematic cross-sectional view of a liquid crystal displaydevice of Example 6.

FIG. 26 is a simulation result of the transmittance viewing angle in theblack display state of the liquid crystal display device of Example 6.

FIG. 27 is a schematic cross-sectional view of a liquid crystal displaydevice of Example 7.

FIG. 28 is a simulation result of the transmittance viewing angle in theblack display state of the liquid crystal display device of Example 7.

FIG. 29 is a schematic cross-sectional view of a liquid crystal displaydevice of Example 8.

FIG. 30 is a simulation result of the transmittance viewing angle in theblack display state of the liquid crystal display device of Example 8.

FIG. 31 is a schematic cross-sectional view of a liquid crystal displaydevice of Example 9.

FIG. 32 is a simulation result of the transmittance viewing angle in theblack display state of the liquid crystal display device of Example 9.

FIG. 33 is a schematic cross-sectional view of a liquid crystal displaydevice of Example 10.

FIG. 34 is a simulation result of the transmittance viewing angle in theblack display state of the liquid crystal display device of Example 10.

FIG. 35 is a schematic cross-sectional view of a liquid crystal displaydevice of Comparative Embodiment 1.

FIG. 36 is a schematic cross-sectional view of a liquid crystal displaydevice of Comparative Embodiment 2.

FIG. 37 is a simulation result of the transmittance viewing angle in theblack display state of the liquid crystal display device of ComparativeEmbodiment 1.

FIG. 38 is a simulation result of the transmittance viewing angle in theblack display state of the liquid crystal display device of ComparativeEmbodiment 2.

FIG. 39 is a schematic cross-sectional view of a liquid crystal displaydevice of Comparative Example 1.

FIG. 40 is a simulation result of the transmittance viewing angle in theblack display state of the liquid crystal display device of ComparativeExample 1.

FIG. 41 is a schematic cross-sectional view of a liquid crystal displaydevice of Comparative Example 2.

FIG. 42 is a simulation result of the transmittance viewing angle in theblack display state of the liquid crystal display device of ComparativeExample 2.

FIG. 43 is a schematic cross-sectional view of a liquid crystal displaydevice of Comparative Example 3.

FIG. 44 is a simulation result of the transmittance viewing angle in theblack display state of the liquid crystal display device of ComparativeExample 3.

FIG. 45 is a schematic cross-sectional view of a liquid crystal displaydevice of Comparative Example 4.

FIG. 46 is a simulation result of the transmittance viewing angle in theblack display state of the liquid crystal display device of ComparativeExample 4.

FIG. 47 is a schematic cross-sectional view of a liquid crystal displaydevice of Comparative Example 5.

FIG. 48 is a simulation result of the transmittance viewing angle in theblack display state of the liquid crystal display device of ComparativeExample 5.

FIG. 49 is a schematic cross-sectional view of a liquid crystal displaydevice of Comparative Example 6.

FIG. 50 is a simulation result of the transmittance viewing angle in theblack display state of the liquid crystal display device of ComparativeExample 6.

FIG. 51 is a schematic cross-sectional view of a liquid crystal displaydevice of Comparative Example 7.

FIG. 52 is a simulation result of the transmittance viewing angle in theblack display state of the liquid crystal display device of ComparativeExample 7.

FIG. 53 is a schematic cross-sectional view of a liquid crystal displaydevice of Comparative Example 8.

FIG. 54 is a simulation result of the transmittance viewing angle in theblack display state of the liquid crystal display device of ComparativeExample 8.

FIG. 55 is a schematic cross-sectional view of a liquid crystal displaydevice of Comparative Example 9.

FIG. 56 is a simulation result of the transmittance viewing angle in theblack display state of the liquid crystal display device of ComparativeExample 9.

FIG. 57 is a schematic cross-sectional view of a liquid crystal displaydevice of Comparative Example 10.

FIG. 58 is a simulation result of the transmittance viewing angle in theblack display state of the liquid crystal display device of ComparativeExample 10.

DETAILED DESCRIPTION OF THE INVENTION

Liquid crystal display devices of embodiments of the present inventionare described below. The embodiments, however, are not intended to limitthe scope of the present invention, and modifications can beappropriately made to the design within the scope of the presentinvention. Features described in the embodiments may appropriately becombined or modified within the spirit of the present invention.

Definitions of Terms and Symbols

Definitions of terms and symbols used herein are as follows.

(1) Refractive Index (nx, ny, nz)

The symbol “nx” represents the refractive index in the direction atwhich the in-plane refractive index is maximum (i.e., slow axisdirection). The symbol “ny” represents the refractive index in thedirection perpendicular to the slow axis in a plane. The symbol “nz”represents the refractive index in the thickness direction. Therefractive indices herein each indicate the value to light with awavelength of 550 nm at 23° C., unless otherwise stated.

(2) In-Plane Retardation (Re)

The in-plane retardation (Re) herein indicates the in-plane retardationof a layer (film) to light with a wavelength of 550 nm at 23° C., unlessotherwise stated. Re is determined by Re=(nx−ny)×d, wherein d is thethickness (nm) of the layer (film).

(3) Thickness Retardation (Rth)

The thickness retardation (Rth) herein indicates the thicknessretardation of a layer (film) to light with a wavelength of 550 nm at23° C., unless otherwise stated. Rth is determined byRth={(nx+ny)/2−nz}×d, wherein d is the thickness (nm) of the layer(film).

(4) NZ Coefficient

The NZ coefficient is determined by NZ=(nx−nz)/(nx−ny) and is a valueshowing the ratio between two axes of a retarder.

(5) λ/4 Plate

The λ/4 plate means a retarder that provides an in-plane retardation of¼ wavelength (137.5 nm, precisely) to at least light having a wavelengthof 550 nm, and may be a retarder that provides an in-plane retardationof 100 nm or greater and 176 nm or smaller. Light having a wavelength of550 nm is light of a wavelength at which a human has the highest visualsensitivity.

(6) λ/2 Plate

The λ/2 plate means a retarder that provides an in-plane retardation of½ wavelength (275 nm, precisely) to at least light having a wavelengthof 550 nm, and may be a retarder that provides an in-plane retardationof 230 nm or greater and 320 nm or smaller.

(7) Circularly Polarizing Plate

The circularly polarizing plate is a polarizing plate that convertsincident unpolarized light into circularly polarized light. Thecircularly polarized light herein encompasses not only perfectlycircularly polarized light (ellipticity (minor axis/major axis)=1.00)but also elliptically polarized light having an ellipticity of 0.90 orgreater and smaller than 1.00.

(8) Viewing Surface Side and Back Surface Side

The viewing surface side means the side closer to the screen (displaysurface) of a liquid crystal display device. The back surface side meansthe side remote from the screen (display surface) of a liquid crystaldisplay device.

(9) Polarizer

The “polarizer” without “linear” herein means a linear polarizer, whichis distinguished from a circular polarizer (circularly polarizingplate).

(10) Polar Angle, Azimuth, Azimuth Angle

FIG. 1 is a figure for illustrating the definitions of a polar angle andan azimuth angle in a liquid crystal display device. As shown in FIG. 1,with the normal direction E of a liquid crystal display device made as areference, the polar angle θ is an angle formed by the measurementdirection F and the normal direction E and is usually 0° or greater and90° or smaller. The direction G that is a projection of the measurementdirection F is defined as the azimuth, which is usually at 0° or greaterand 360° or smaller. The angle from a reference direction on the screen(azimuth angle 0°) to the direction G is defined as the azimuth angle ϕ.The azimuth angle ϕ is defined to be positive in the counterclockwisedirection and to be negative in the clockwise direction. The termscounterclockwise and clockwise each indicate a direction when the screenis viewed from the viewing surface side (front). The polar angle θ isalso simply referred to as a polar angle. The azimuth angle ϕ is alsosimply referred to as an azimuth angle and is defined with thehorizontal direction of the screen as a reference (0°).

Embodiment 1

FIG. 2 is a schematic cross-sectional view of a liquid crystal displaydevice of Embodiment 1. A liquid crystal display device 1 of the presentembodiment includes, in the following order from the viewing surfaceside, a first polarizer 1P, a first positive A plate 1A having anin-plane retardation of 120 nm or greater and 155 nm or smaller, apositive C plate 1C having a thickness retardation of 80 nm or greaterand 100 nm or smaller, a first substrate 100, a second positive A plate2A having an in-plane retardation of 120 nm or greater and 155 nm orsmaller, a horizontally aligned liquid crystal layer 1L, a secondsubstrate 200, a viewing angle compensation layer 30, and a secondpolarizer 2P. The liquid crystal display device 1 further includesbetween the first polarizer 1P and the first positive A plate 1A apositive C plate 11C having a thickness retardation of 30 nm or greaterand 80 nm or smaller.

The first substrate 100 includes, in the following order from theviewing surface side, an insulating substrate formed from a transparentmaterial such as glass and a color filter (CF) layer. The CF layerincludes color filters and a black matrix. The color filters include,for example, red color filters, green color filters, and blue colorfilters. The first substrate 100 is also referred to as a CF substrate.

The second substrate 200 includes, in the following order toward theliquid crystal layer 1L, an insulating substrate, scanning lines, datalines, thin film transistors (TFTs) connected to the scanning lines andthe data lines, and an electrode layer. The electrode layer includes, inthe following order toward the liquid crystal layer 1L, a planar commonelectrode, an insulating film, and pixel electrodes with slits. Thepositions of the common electrode and the pixel electrodes may beswitched, and a common electrode with slits may be formed on the liquidcrystal layer 1L side of planar pixel electrodes. The second substrate200 is also referred to as a TFT substrate.

The pixel electrodes each have a potential in accordance with a datasignal supplied through the corresponding TFT. A fringe electric fieldis generated between the pixel electrodes and the common electrode torotate liquid crystal molecules in the liquid crystal layer. The voltageapplied between the pixel electrodes and the common electrode iscontrolled to change the retardation of the liquid crystal layer,whereby light is controlled to be transmitted or not transmitted. Theliquid crystal display device 1 of the present embodiment is a fringefield switching (FFS) mode liquid crystal display device.

Although the present embodiment exemplifies a FFS mode liquid crystaldisplay device 1, the present embodiment may be applied to an in-planeswitching (IPS) mode liquid crystal display device in which each ofpixel electrodes as comb-teeth electrodes and a common electrode as acomb-teeth electrode are formed on the same electrode layer such thattheir comb teeth fit each other.

The absorption axis of the first polarizer 1P is set to form an angle ofabout 90° with the absorption axis of the second polarizer 2P. Thisstructure suitably achieves the black display state with no voltageapplied (when the voltage applied to the liquid crystal layer is lessthan the threshold value).

The first polarizer 1P and the second polarizer 2P may each be anypolarizer appropriate for the object. Examples thereof include thoseobtained by adsorbing a dichroic substance (dichroic pigment), such asiodine or a dichroic dye, to a hydrophilic polymer film, such as apolyvinyl alcohol film, a partially formalized polyvinyl alcohol film,or an ethylene-vinyl acetate copolymer-based partially saponified film,and uniaxially stretching the film; and polyene-based alignment filmssuch as a dehydrated product of polyvinyl alcohol and adehydrochlorinated product of polyvinyl chloride. Particularly preferredamong these is a polarizer obtained by adsorbing a dichroic substance(dichroic pigment) such as iodine to a polyvinyl alcohol film anduniaxially stretching the film because such a polarizer has a highpolarized dichroic ratio. The thickness of such a polarizer is notlimited and may usually be about 5 to 30 μm.

In the case where the liquid crystal display device 1 including thehorizontally aligned liquid crystal layer 1L includes the firstpolarizer 1P and the second polarizer 2P with their absorption axesarranged to form an angle of about 90° when viewed from the viewingsurface side, i.e., in the case where the first polarizer 1P and thesecond polarizer 2P are arranged in the crossed Nicols, the absorptionaxes have axial dislocation from the crossed Nicols arrangement whenviewed from an oblique direction. In order to correct this axialdislocation, the liquid crystal display device 1 of the presentembodiment is provided with a viewing angle compensation film generallyused in the field of liquid crystal display devices as the viewing anglecompensation layer 30. The viewing angle compensation film, even in anoblique direction, can change the polarization state of linearlypolarized light having passed through one of paired polarizers arrangedin the crossed Nicols such that the linearly polarized light ispolarized in the direction parallel to the absorption axis of the otherpolarizer. The viewing angle compensation film may be used in both of aliquid crystal display device including a horizontally aligned liquidcrystal layer and a liquid crystal display device including a verticallyaligned liquid crystal layer. The horizontally aligned liquid crystallayer means a liquid crystal layer in which liquid crystal moleculesalign in the direction substantially parallel to the main surface ofeach of paired substrates with no voltage applied. The expressionsubstantially parallel means, for example, that the tilt angle of liquidcrystal molecules is 0° or greater and 5° or smaller to the main surfaceof each substrate. The tilt angle of liquid crystal molecules means anangle of inclination of the major axes (optical axes) of liquid crystalmolecules to the surface of a substrate. The vertically aligned liquidcrystal layer means a liquid crystal layer in which liquid crystalmolecules align in the direction substantially perpendicular to the mainsurface of each of paired substrates with no voltage applied. Theexpression substantially perpendicular means, for example, that the tiltangle of liquid crystal molecules is 85° or greater and 90° or smallerto the main surface of each substrate.

The first positive A plate 1A is a λ/4 plate. A laminate including thefirst positive A plate 1A and the positive C plate 1C is also referredto as the out-cell retardation layer 21. The second positive A plate 2Ais a λ/4 plate and is also referred to as the in-cell retardation layer22.

In the present embodiment, the out-cell retardation layer 21 is disposedin combination with the first polarizer 1P to function as a circularlypolarizing plate, which can reduce reflection of external light.Accordingly, the in-plane retardation of the first positive A plate 1Ain the out-cell retardation layer 21 is set to 120 nm or greater and 155nm or smaller, and the slow axis of the first positive A plate 1A is setto form an angle of about 45° with the absorption axis of the firstpolarizer 1P.

The in-plane retardation of the second positive A plate 2A that is thein-cell retardation layer 22 is set to 120 nm or greater and 155 nm orsmaller. The slow axis of the second positive A plate 2A is set to forman angle of about 90° with the slow axis of the first positive A plate1A. Thereby, at least in the front direction, the out-cell retardationlayer 21 and the in-cell retardation layer 22 can cancel out the eachother's retardations in the in-plane direction to achieve a state wherethe out-cell retardation layer 21 and the in-cell retardation layer 22substantially do not exist. This structure resultantly providestransmissive display with similar optical properties to those of atypical FFS mode device while achieving low reflection.

In order to cancel the retardation of the in-cell retardation layer 22formed from the second positive A plate 2A at all the azimuths, theout-cell retardation layer 21 may be formed from a negative A plate.Unfortunately, materials for the negative A plate tend to be torn, i.e.,are fragile. The liquid crystal display device 1 of the presentembodiment employs a laminate including the first positive A plate 1Aand the positive C plate 1C as the out-cell retardation layer 21 so thatthe out-cell retardation layer 21 works as a negative A plate inappearance, which can prevent deterioration in fragileness of theout-cell retardation layer 21.

Differently from the negative A plate, the out-cell retardation layer 21that is a laminate including the first positive A plate 1A and thepositive C plate 1C cannot completely cancel the retardation of thesecond positive A plate 2A at almost all the azimuths. Thus, in theliquid crystal display device 1 of the present embodiment, which employsthe viewing angle compensation layer 30 together with the out-cellretardation layer 21 and the in-cell retardation layer 22, linearlypolarized light having passed through the second polarizer 2P becomespolarized light that is polarized at the same azimuth as that of theabsorption axis of the first polarizer 1P. This polarized light behavesnot as linearly polarized light but as slightly elliptically polarizedlight when viewed from oblique directions, which unfortunately causeslight leakage when viewed from oblique directions in the black displaystate.

In the present embodiment, the positive C plate 11C having a thicknessretardation of 30 nm or greater and 80 nm or smaller is further disposedbetween the first polarizer 1P and the first positive A plate 1A toconvert the elliptically polarized light into linearly polarized light,which can further suppress the light leakage when viewed from obliquedirections in the black display state.

The positive C plate 11C has a thickness retardation of preferably 35 nmor greater and 75 nm or smaller, more preferably 40 nm or greater and 70nm or smaller. The positive C plate 11C preferably has an in-planeretardation of substantially 0 nm.

The positive C plate 11C may be formed, for example, by applying avertical alignment film to a substrate formed from a resin such aspolyethylene terephthalate, applying polymerizable liquid crystal to thesubstrate to form a vertically aligned polymerizable liquid crystallayer, and disposing the polymerizable liquid crystal layer in apredetermined position of the liquid crystal panel with an adhesivematerial. The vertical alignment film may or may not be transferred tothe liquid crystal panel side. The vertical alignment film is analignment film that aligns liquid crystal molecules in the liquidcrystal layer in a direction perpendicular to the surface of thevertical alignment film with no voltage applied.

The first positive A plate 1A has an in-plane retardation of preferably125 nm or greater and 150 nm or smaller, more preferably 130 nm orgreater and 145 nm or smaller.

The first positive A plate 1A has an NZ coefficient of preferably 0.8 orgreater and 1.3 or smaller, more preferably 0.9 or greater and 1.2 orsmaller.

Specific examples of the first positive A plate 1A include a retardationlayer including a liquid crystal compound with fixed alignment, and aretardation layer obtained by stretching a resin film for a positive Aplate.

The retardation layer including a liquid crystal compound with fixedalignment is described. A specific example of the retardation layerincluding a liquid crystal compound with fixed alignment is aretardation layer that includes a film (alignment film) after alignmenttreatment and a liquid crystal material, such as a reactive mesogen,whose molecules are aligned on the film. An example of the method forforming such a retardation layer is a method including applying a liquidcrystal material including a liquid crystal compound to a substrate filmafter alignment treatment and fixing the alignment of molecules of theliquid crystal compound. A suitable example of the liquid crystalcompound is polymerizable liquid crystal. Any method can be employed aslong as the desired retardation is achieved, including a methodperforming no special alignment treatment on a substrate film and amethod including fixing the alignment of molecules of a liquid crystalcompound and separating the compound layer from a substrate film andtransferring the compound layer to a different film. Also, a methodwithout fixing the alignment of molecules of a liquid crystal materialmay be employed.

The polymerizable liquid crystal means a compound containing apolymerizable group and having properties of liquid crystal. Thepolymerizable group means a group that is involved in a polymerizationreaction and is preferably a photopolymerizable group. Thephotopolymerizable group means a group that can be involved in apolymerization reaction using an active radical or acid generated from aphotopolymerization initiator. Examples of the polymerizable groupinclude vinyl, vinyloxy, 1-chlorovinyl, isopropenyl, 4-vinylphenyl,acryloyloxy, methacryloyloxy, oxiranyl, and oxetanyl groups. Preferredamong these are acryloyloxy, methacryloyloxy, vinyloxy, oxiranyl, andoxetanyl groups, and more preferred is an acryloyloxy group. Thepolymerizable liquid crystal may be a thermotropic liquid crystal or alyotropic liquid crystal. When thermotropic liquid crystals arecategorized according the degree of order, a nematic liquid crystal or asmectic liquid crystal may be employed. Still, a thermotropic nematicliquid crystal is preferred in terms of easiness of film formation.

Specific examples of the polymerizable liquid crystal include compoundshaving a polymerizable group among the compounds disclosed in “3.8.6Network (completely cross-linked type)” and “6.5.1 Liquid crystalmaterial b. Polymerizable nematic liquid crystal material” of LiquidCrystal Handbook (Ekisho Binran), the LCD Handbook Editorial Committee(Ekisho Binran Hensyu Iinkai), Maruzen Co., Ltd., published on Oct. 30,2000); and polymerizable liquid crystals disclosed in JP 2010-31223 A,JP 2010-270108 A, JP 2011-6360 A, and JP 2011-207765 A.

The retardation layer obtained by stretching a resin film for a positiveA plate is described. Examples of the material of the resin film for apositive A plate include acyclic polyolefins such as polypropylenes,cyclic polyolefins such as polynorbornenes, celluloses such as cellulosetriacetate and cellulose diacetate, polyesters, polycarbonates,polyacrylates, polymethacrylates, polystyrenes, liquid crystalcompositions, and mixtures and copolymers of these. Examples of theresin film for a positive A plate using a cyclic polyolefin as amaterial include “Zeonor®” available from Zeon Corporation.

The positive C plate 1C has a thickness retardation of preferably 82 nmor greater and 98 nm or smaller, more preferably 85 nm or greater and 95nm or smaller. The positive C plate 1C preferably has an in-planeretardation of substantially 0 nm.

The positive C plate 1C may be formed by the same method as for thepositive C plate 11C.

The second positive A plate 2A has an in-plane retardation of preferably125 nm or greater and 150 nm or smaller, more preferably 130 nm orgreater and 145 nm or smaller.

The second positive A plate 2A has an NZ coefficient of preferably 0.8or greater and 1.3 or smaller, more preferably 0.9 or greater and 1.2 orsmaller.

The second positive A plate 2A is preferably the retardation layerincluding a liquid crystal compound with fixed alignment, which has beengiven as a specific example of the first positive A plate 1A. Thisstructure can reduce the thickness of the in-cell retardation layer 22that is a positive A plate, and thereby can suppress color mixing causedby parallax of the liquid crystal display device 1.

The horizontally aligned liquid crystal layer 1L includes liquid crystalmolecules. The liquid crystal molecules may have a positive or negativeanisotropy of dielectric constant (As) defined by the following formula.Liquid crystal molecules having a positive anisotropy of dielectricconstant are also referred to as positive liquid crystals and liquidcrystal molecules having a negative anisotropy of dielectric constantare also referred to as negative liquid crystal. The direction of themajor axis of liquid crystal molecules corresponds to the direction ofthe slow axis thereof.

Δε=(dielectric constant in the major axis direction)−(dielectricconstant in the minor axis direction)

In the horizontally aligned liquid crystal layer 1L, in order tosuppress light leakage in the black display state, the alignment azimuthof the liquid crystal molecules to which a voltage for providing blackdisplay is applied (in the black display state) forms an angle of about90° with the absorption axis of the first polarizer 1P or the secondpolarizer 2P, and in order to achieve a better transmittance in thewhite display state, the alignment azimuth of the liquid crystalmolecules to which a voltage for providing white display is applied (inthe white display state) forms an angle of about 45° with the alignmentazimuth of the liquid crystal molecules in the black display state.Here, the viewing angle compensation layer 30 is not disposed betweenthe liquid crystal layer 1L and one of the first polarizer 1P or thesecond polarizer 2P (hereinafter, also referred to as a specificpolarizer), whichever has an absorption axis forming an angle of about0° with the alignment azimuth of the liquid crystal molecules. Since theabsorption axis of the specific polarizer and the alignment azimuth ofthe liquid crystal molecules form an angle of about 0°, the angle formedby the alignment azimuth of the liquid crystal molecules and theabsorption axis of the specific polarizer remains at about 0° even whenthe device is viewed from the normal direction E or from an obliquedirection (e.g., a direction at a polar angle of 60° and an azimuthangle of) 45°. This structure thus can allow the liquid crystal layer 1Lto cause no retardation even when viewed from oblique directions. Here,if the viewing angle compensation layer 30 is disposed between thespecific polarizer and the liquid crystal layer 1L, the polarizationstate changes between the specific polarizer and the liquid crystallayer 1L. As a result, the liquid crystal layer 1L unfortunatelyfunctions as a retarder when viewed from oblique directions to causelight leakage. Therefore, no viewing angle compensation layer 30 isdisposed between the specific polarizer and the liquid crystal layer 1L.In other words, the viewing angle compensation layer 30 is disposedbetween the liquid crystal layer 1L and one of the first polarizer 1P orthe second polarizer 2P, whichever has an absorption axis forming anangle of about 90° with the alignment azimuth of the liquid crystalmolecules.

The angle about 0° herein may fall within the range of 0°±3°, preferablywithin the range of 0°±1°, more preferably within the range of 0°±0.5°,particularly preferably 0°. The angle about 45° herein may fall withinthe range of 45°±3°, preferably within the range of 45°±1°, morepreferably within the range of 45°±0.5°, particularly preferably 45°.The angle about 90° herein may fall within the range of 90°±3°,preferably within the range of 90°±1°, more preferably within the rangeof 90°±0.5°, particularly preferably 90°.

The following Embodiments 1-1 to 1-4 describe the liquid crystal displaydevice 1 with reference to specific examples of the viewing anglecompensation layer 30 of the present embodiment.

Embodiment 1-1

FIG. 3 is a schematic cross-sectional view of a liquid crystal displaydevice of Embodiment 1-1. As shown in FIG. 3, the viewing anglecompensation layer 30 in a liquid crystal display device 1 of thepresent embodiment is a first laminate 31 including, in the followingorder from the second polarizer 2P side, a positive A plate 31A havingan in-plane retardation of 130 nm or greater and 150 nm or smaller and apositive C plate 31C having a thickness retardation of 80 nm or greaterand 100 nm or smaller.

The positive A plate 31A has an in-plane retardation of preferably 132nm or greater and 148 nm or smaller, more preferably 135 nm or greaterand 145 nm or smaller.

The positive A plate 31A has an NZ coefficient of preferably 0.8 orgreater and 1.2 or smaller, more preferably 0.9 or greater and 1.1 orsmaller.

The positive A plate 31A may be formed by the same method as for thepositive A plate 1A.

The positive C plate 31C has a thickness retardation of preferably 82 nmor greater and 98 nm or smaller, more preferably 85 nm or greater and 95nm or smaller. The positive C plate 31C preferably has an in-planeretardation of substantially 0 nm.

The positive C plate 31C may be formed by the same method as for thepositive C plate 11C.

The slow axis of the positive A plate 31A in the first laminate 31preferably forms an angle of about 90° with the absorption axis of theadjacent polarizer, i.e., the second polarizer 2P. In the case where theslow axis of the positive A plate 31A is set to form an angle of about0° with the absorption axis of the second polarizer 2P, the angle formedby the absorption axis of the second polarizer 2P and the slow axis ofthe positive A plate 31A remains at about 0° when the liquid crystaldisplay device 1 is viewed from the normal direction E and from anoblique direction (e.g., a direction at a polar angle of 60° and anazimuth angle of 45°). Thus, linearly polarized light having passedthrough the second polarizer 2P is incident on only the fast axis of thepositive A plate 31A to cause no change in retardation, resulting in asimilar state to the state where no positive A plate 31A is disposed.Meanwhile, in the case where the slow axis of the positive A plate 31Ais set to form an angle of about 90° with the absorption axis of thesecond polarizer 2P and the liquid crystal display device 1 is viewedfrom the normal direction E, linearly polarized light having passedthrough the second polarizer 2P is incident on the positive A plate 31Aat the azimuth of the slow axis thereof to cause no retardation and nochange in the polarization state. In contrast, when the liquid crystaldisplay device 1 is viewed from an oblique direction (e.g., a directionat a polar angle of 60° and an azimuth angle of 45°), the angle formedby the absorption axis of the second polarizer 2P and the slow axis ofthe positive A plate 31A is shifted from the angle having set to about90° to cause a retardation and change the polarization state, wherebythe viewing angle can be compensated.

Embodiment 1-2

FIG. 4 is a schematic cross-sectional view of a liquid crystal displaydevice of Embodiment 1-2. As shown in FIG. 4, the viewing anglecompensation layer 30 in a liquid crystal display device 1 of thepresent embodiment is a second laminate 32 including, in the followingorder from the second polarizer 2P side, a biaxial retardation layer32T1 having an in-plane retardation of 80 nm or greater and 100 nm orsmaller and an NZ coefficient of 1.3 or greater and 1.5 or smaller and abiaxial retardation layer 32T2 having an in-plane retardation of 50 nmor greater and 70 nm or smaller and an NZ coefficient of −1.2 or greaterand −0.8 or smaller.

The biaxial retardation layer 32T1 may be formed by simultaneous biaxialstretching or sequential biaxial stretching on a material with apositive birefringence, for example. Specific examples of the materialwith a positive birefringence include the same as the examples for thematerials of the resin film for a positive A plate.

The biaxial retardation layer 32T2 may be formed by simultaneous biaxialstretching or sequential biaxial stretching on a material with anegative birefringence, for example. Examples of the material with anegative birefringence include polymers containing at a side chainthereof a chemical bond or a functional group having large polarizationanisotropy, such as an aromatic group and a carbonyl group, and specificexamples thereof include polyacrylate, polymethacrylate, polystyrene,polymaleimide, and polyfumaric acid esters.

The biaxial retardation layer 32T1 preferably has an in-planeretardation of 82 nm or greater and 98 nm or smaller and an NZcoefficient of 1.32 or greater and 1.48 or smaller, and more preferablyhas an in-plane retardation of 85 nm or greater and 95 nm or smaller andan NZ coefficient of 1.35 or greater and 1.45 or smaller.

The biaxial retardation layer 32T2 preferably has an in-planeretardation of 52 nm or greater and 68 nm or smaller and an NZcoefficient of −1.22 or greater and −0.78 or smaller, and morepreferably has an in-plane retardation of 55 nm or greater and 65 nm orsmaller and an NZ coefficient of −1.25 or greater and −0.75 or smaller.

The slow axes of the two biaxial retardation layers 32T1 and 32T2 in thesecond laminate 32 each preferably form an angle of about 90° with theabsorption axis of the adjacent polarizer, i.e., the second polarizer2P, for the same reason why the slow axis of the positive A plate 31A inthe first laminate 31 preferably forms an angle of about 90° with theabsorption axis of the adjacent polarizer, i.e., the second polarizer2P, in Embodiment 1-1.

Embodiment 1-3

FIG. 5 is a schematic cross-sectional view of a liquid crystal displaydevice of Embodiment 1-3. As shown in FIG. 5, the viewing anglecompensation layer 30 in a liquid crystal display device 1 of thepresent embodiment is a third laminate 33 including, in the followingorder from the second polarizer 2P side, a biaxial retardation layer33T1 having an in-plane retardation of 100 nm or greater and 130 nm orsmaller and an NZ coefficient of 1.1 or greater and 1.3 or smaller and abiaxial retardation layer 33T2 having an in-plane retardation of 10 nmor greater and 30 nm or smaller and an NZ coefficient of −4.5 or greaterand −3.5 or smaller.

The biaxial retardation layer 33T1 may be formed by the same method asfor the biaxial retardation layer 32T1. The biaxial retardation layer33T2 may be formed by the same method as for the biaxial retardationlayer 32T2.

The biaxial retardation layer 33T1 preferably has an in-planeretardation of 105 nm or greater and 125 nm or smaller and an NZcoefficient of 1.12 or greater and 1.28 or smaller, and more preferablyhas an in-plane retardation of 110 nm or greater and 120 nm or smallerand an NZ coefficient of 1.15 or greater and 1.25 or smaller.

The biaxial retardation layer 33T2 preferably has an in-planeretardation of 12 nm or greater and 28 nm or smaller and an NZcoefficient of −4.4 or greater and −3.6 or smaller, and more preferablyhas an in-plane retardation of 15 nm or greater and 25 nm or smaller andan NZ coefficient of −4.3 or greater and −3.5 or smaller.

The slow axes of the two biaxial retardation layers 33T1 and 33T2 in thethird laminate 33 each preferably form an angle of about 90° with theabsorption axis of the adjacent polarizer, i.e., the second polarizer2P, for the same reason why the slow axis of the positive A plate 31A inthe first laminate 31 preferably forms an angle of about 90° with theabsorption axis of the adjacent polarizer, i.e., the second polarizer2P, in Embodiment 1-1.

Embodiment 1-4

FIG. 6 is a schematic cross-sectional view of a liquid crystal displaydevice of Embodiment 1-4. As shown in FIG. 6, the viewing anglecompensation layer 30 in a liquid crystal display device 1 of thepresent embodiment is a λ/2 plate 301 having an in-plane retardation of230 nm or greater and 320 nm or smaller and an NZ coefficient of 0.4 orgreater and 0.6 or smaller.

The λ/2 plate 301 may be formed, for example, by applying a coating filmliquid in which a resin is dissolved or dispersed in a solvent to ashrinkable film to form a coating film and shrinking the coating film.The coating film may be shrunk by, for example, heating the laminateincluding the shrinkable film and the coating film to shrink theshrinkable film and thereby shrinking the coating film. Examples of theresin include polyarylate, polyamide, polyimide, polyester, polyarylether ketone, polyamide imide, polyester imide, polyvinyl alcohol,polyfumaric acid ester, polyethersulfone, polysulfone, polynorbornene,polycarbonate, cellulose, and polyurethane. These polymers may be usedalone or in combination. Specific examples of the material for theshrinkable film include polyolefins (cyclic polyolefins and acyclicpolyolefins, preferably acyclic polyolefins), polyester, polyacrylate,polymethacrylate, polyamide, polycarbonate, polynorbornene, polystyrene,polyvinyl chloride, polyvinylidene chloride, cellulose,polyethersulfone, polysulfone, polyimide, polyacetate, polyarylate,polyvinyl alcohol, and liquid crystal polymers. These may be used aloneor in combination. More specifically, the λ/2 plate 301 may be formed bythe method disclosed in the paragraphs 0061 and 0063 in JP 2017-181735A.

Alternatively, the λ/2 plate 301 may be formed by stretching a polymerfilm. Specific examples of the material for the polymer film includeacyclic polyolefins such as polycarbonate and polypropylene, polyesterssuch as polyethylene terephthalate and polyethylene naphthalate, cyclicpolyolefins such as polynorbornene, polyvinyl alcohol, polyvinylbutyral, polymethyl vinyl ether, polyhydroxyethyl acrylate, hydroxyethylcellulose, hydroxypropyl cellulose, methyl cellulose, polyarylate,polysulfone, polyethersulfone, polyphenylene sulfide, polyphenyleneoxide, polyallyl sulfone, polyvinyl alcohol, polyamide, polyimide,polyvinyl chloride, and cellulose. These may be used alone or incombination. More specifically, the λ/2 plate 301 may be formed bystretching a polycarbonate film in the manner as described in theparagraph 0123 in JP 2004-325468 A.

The λ/2 plate 301 preferably has an in-plane retardation of 240 nm orgreater and 310 nm or smaller and an NZ coefficient of 0.42 or greaterand 0.58 or smaller, and more preferably has an in-plane retardation of250 nm or greater and 300 nm or smaller and an NZ coefficient of 0.45 orgreater and 0.55 or smaller.

The slow axis of the λ/2 plate 301 preferably forms an angle of about90° with the absorption axis of the adjacent polarizer, i.e., the secondpolarizer 2P, for the same reason why the slow axis of the positive Aplate 31A in the first laminate 31 preferably forms an angle of about90° with the absorption axis of the adjacent polarizer, i.e., the secondpolarizer 2P, in Embodiment 1-1.

Embodiment 2

In the present embodiment, the features unique to the present embodimentare mainly described and the same features as those in the aboveembodiment are not described again. Embodiment 1 describes an embodimentin which the viewing angle compensation layer 30 is disposed between thesecond substrate 200 and the second polarizer 2P. The present embodimentdescribes an embodiment in which the viewing angle compensation layer 30is disposed between the first polarizer 1P and the first positive Aplate 1A.

FIG. 7 is a schematic cross-sectional view of a liquid crystal displaydevice of Embodiment 2. A liquid crystal display device 1 of the presentembodiment includes, in the following order from the viewing surfaceside, the first polarizer 1P, the viewing angle compensation layer 30,the first positive A plate 1A having an in-plane retardation of 120 nmor greater and 155 nm or smaller, the positive C plate 1C having athickness retardation of 80 nm or greater and 100 nm or smaller, thefirst substrate 100, the second positive A plate 2A having an in-planeretardation of 120 nm or greater and 155 nm or smaller, the horizontallyaligned liquid crystal layer 1L, the second substrate 200, and thesecond polarizer 2P. The liquid crystal display device 1 furtherincludes, between the viewing angle compensation layer 30 and the firstpositive A plate 1A, the positive C plate 11C having a thicknessretardation of 30 nm or greater and 80 nm or smaller.

In the present embodiment, the first polarizer 1P and the secondpolarizer 2P are arranged in the crossed Nicols as in Embodiment 1.Although this structure causes axial dislocation from the crossed Nicolsformation when the device is viewed from oblique directions, the viewingangle compensation layer 30 can correct the axial dislocation.

In the present embodiment, the out-cell retardation layer 21 is disposedin combination with the first polarizer 1P to function as a circularlypolarizing plate, which can reduce reflection of external light.

Accordingly, the in-plane retardation of the first positive A plate 1Ain the out-cell retardation layer 21 is set to 120 nm or greater and 155nm or smaller, and the slow axis of the first positive A plate 1A is setto form an angle of about 45° with the absorption axis of the firstpolarizer 1P.

The in-plane retardation of the second positive A plate 2A that is thein-cell retardation layer 22 is set to 120 nm or greater and 155 nm orsmaller. The slow axis of the second positive A plate 2A is set to forman angle of about 90° with the slow axis of the first positive A plate1A. Thereby, at least in the front direction, the out-cell retardationlayer 21 and the in-cell retardation layer 22 can cancel out the eachother's retardations in the in-plane direction to achieve a state wherethe out-cell retardation layer 21 and the in-cell retardation layer 22substantially do not exist. This structure resultantly providestransmissive display with similar optical properties to those of atypical FFS mode device while achieving low reflection.

In order to cancel the retardation of the in-cell retardation layer 22formed from the second positive A plate 2A at all the azimuths, theout-cell retardation layer 21 may be formed from a negative A plate asdescribed above. Unfortunately, materials for the negative A plate tendto be torn, i.e., are fragile. The liquid crystal display device 1 ofthe present embodiment employs a laminate including the first positive Aplate 1A and the positive C plate 1C as the out-cell retardation layer21 so that the out-cell retardation layer 21 works as a negative A platein appearance, which can prevent deterioration in fragileness of theout-cell retardation layer 21.

Differently from the negative A plate, the out-cell retardation layer 21that is a laminate including the first positive A plate 1A and thepositive C plate 1C cannot completely cancel the retardation of thesecond positive A plate 2A at almost all the azimuths. Thus, in theliquid crystal display device 1 of the present embodiment, which employsthe viewing angle compensation layer 30 together with the out-cellretardation layer 21 and the in-cell retardation layer 22, linearlypolarized light having passed through the second polarizer 2P ispolarized at the same azimuth as that of the absorption axis of thefirst polarizer 1P. This polarized light behaves as not linearlypolarized light but slightly elliptically polarized light when viewedfrom oblique directions, which unfortunately causes light leakage whenviewed from oblique directions in the black display state.

In the present embodiment, the positive C plate 11C having a thicknessretardation of 30 nm or greater and 80 nm or smaller is further disposedbetween the viewing angle compensation layer 30 and the first positive Aplate 1A to convert the elliptically polarized light into linearlypolarized light, which can further suppress the light leakage whenviewed from oblique directions in the black display state.

The following Embodiments 2-1 to 2-4 describe the liquid crystal displaydevice 1 with reference to specific examples of the viewing anglecompensation layer 30 of the present embodiment.

Embodiment 2-1

FIG. 8 is a schematic cross-sectional view of a liquid crystal displaydevice of Embodiment 2-1. As shown in FIG. 8, the viewing anglecompensation layer 30 in a liquid crystal display device 1 of thepresent embodiment is a first laminate 31 including, in the followingorder from the first polarizer 1P side, the positive A plate 31A and thepositive C plate 31C that are used in Embodiment 1-1.

The slow axis of the positive A plate 31A in the first laminate 31preferably forms an angle of about 90° with the absorption axis of theadjacent polarizer, i.e., the first polarizer 1P, for the same reasonwhy the slow axis of the positive A plate 31A in the first laminate 31preferably forms an angle of about 90° with the absorption axis of theadjacent polarizer, i.e., the second polarizer 2P, in Embodiment 1-1.

Embodiment 2-2

FIG. 9 is a schematic cross-sectional view of a liquid crystal displaydevice of Embodiment 2-2. As shown in FIG. 9, the viewing anglecompensation layer 30 in a liquid crystal display device 1 of thepresent embodiment is a second laminate 32 including, in the followingorder from the first polarizer 1P side, the biaxial retardation layer32T1 and the biaxial retardation layer 32T2 that are used in Embodiment1-2.

The slow axes of the two biaxial retardation layers 32T1 and 32T2 in thesecond laminate 32 preferably each form an angle of about 90° with theabsorption axis of the adjacent polarizer, i.e., the first polarizer 1P,for the same reason why the slow axis of the positive A plate 31A in thefirst laminate 31 preferably forms an angle of about 90° with theabsorption axis of the adjacent polarizer, i.e., the second polarizer2P, in Embodiment 1-1.

Embodiment 2-3

FIG. 10 is a schematic cross-sectional view of a liquid crystal displaydevice of Embodiment 2-3. As shown in FIG. 10, the viewing anglecompensation layer 30 in a liquid crystal display device 1 of thepresent embodiment is a third laminate 33 including, in the followingorder from the first polarizer 1P side, the biaxial retardation layer33T1 and the biaxial retardation layer 33T2 that are used in Embodiment1-3.

The slow axes of the two biaxial retardation layers 33T1 and 33T2 in thethird laminate 33 preferably each form an angle of about 90° with theabsorption axis of the adjacent polarizer, i.e., the first polarizer 1P,for the same reason why the slow axis of the positive A plate 31A in thefirst laminate 31 preferably forms an angle of about 90° with theabsorption axis of the adjacent polarizer, i.e., the second polarizer2P, in Embodiment 1-1.

Embodiment 2-4

FIG. 11 is a schematic cross-sectional view of a liquid crystal displaydevice of Embodiment 2-4. As shown in FIG. 11, the viewing anglecompensation layer 30 in a liquid crystal display device 1 of thepresent embodiment is the λ/2 plate 301 that is used in Embodiment 1-4.

The slow axis of the λ/2 plate 301 preferably forms an angle of about90° with the absorption axis of the adjacent polarizer, i.e., the firstpolarizer 1P, for the same reason why the slow axis of the positive Aplate 31A in the first laminate 31 preferably forms an angle of about90° with the absorption axis of the adjacent polarizer, i.e., the secondpolarizer 2P, in Embodiment 1-1.

Embodiment 3

In the present embodiment, the features unique to the present embodimentare mainly described and the same features as those in the aboveembodiment are not described again. The liquid crystal display device ofthe present embodiment has the same structure as the liquid crystaldisplay device 1 of Embodiment 2-1 except that the positive C plate 11Cand the positive C plate 31C are integrated into one layer (thelater-described positive C plate 12C having a thickness retardation of130 nm or greater and 160 nm or smaller). The following is descriptionin detail.

FIG. 12 is a schematic cross-sectional view of a liquid crystal displaydevice of Embodiment 3. As shown in FIG. 12, a liquid crystal displaydevice 1 of the present embodiment includes, in the following order fromthe viewing surface side, the first polarizer 1P, a viewing anglecompensation layer 30A, the first positive A plate 1A having an in-planeretardation of 120 nm or greater and 155 nm or smaller, the positive Cplate 1C having a thickness retardation of 80 nm or greater and 100 nmor smaller, the first substrate 100, the second positive A plate 2Ahaving an in-plane retardation of 120 nm or greater and 155 nm orsmaller, the horizontally aligned liquid crystal layer 1L, the secondsubstrate 200, and the second polarizer 2P. The viewing anglecompensation layer 30A is the positive A plate 31A having an in-planeretardation of 130 nm or greater and 150 nm or smaller. The liquidcrystal display device 1 further includes, between the viewing anglecompensation layer 30A and the first positive A plate 1A, a positive Cplate 12C having a thickness retardation of 130 nm or greater and 160 nmor smaller.

The liquid crystal display device 1 of the present embodiment has thesame structure as the liquid crystal display device 1 of Embodiment 2-1except that the positive C plate 11C and the positive C plate 31C in theliquid crystal display device 1 of Embodiment 2-1 are integrated intothe positive C plate 12C. In other words, the liquid crystal displaydevice 1 of the present embodiment is optically equal to the liquidcrystal display device 1 of Embodiment 2-1 and, similarly to Embodiment2-1, can prevent deterioration in fragileness of the out-cellretardation layer 21, reflection of external light, and light leakagewhen viewed from oblique directions in the black display state. Thepresent embodiment, which employs a structure in which the positive Cplate 11C and the positive C plate 31C are integrated, can eliminate anadhesive layer to reduce the thickness of the positive C plate 12C. Thepresent embodiment, which reduces the number of layers laminated andthereby reduces production steps, can also reduce the costs. An increasein the number of layers to be laminated may reduce the yield because ofcontamination by foreign substances. Such a reduction in yield isavoidable by integrating the positive C plate 11C and the positive Cplate 31C and thereby reducing the number of layers laminated.

The positive C plate 12C may be formed by the same method as for thepositive C plate 11C.

The positive C plate 12C has a thickness retardation of preferably 132nm or greater and 158 nm or smaller, more preferably 135 nm or greaterand 155 nm or smaller. The positive C plate 12C preferably has anin-plane retardation of substantially 0 nm.

Embodiment 4

In the present embodiment, the features unique to the present embodimentare mainly described and the same features as those in the aboveembodiment are not described again. The liquid crystal display device ofthe present embodiment has the same structure as the liquid crystaldisplay device 1 of Embodiment 2-2 except that the positive C plate 11Cand the biaxial retardation layer 32T2 are integrated into one layer(the later-described biaxial retardation layer 13C having an in-planeretardation of 50 nm or greater and 70 nm or smaller and an NZcoefficient of −2.0 or greater and −1.6 or smaller). The following isdescription in detail.

FIG. 13 is a schematic cross-sectional view of a liquid crystal displaydevice of Embodiment 4. As shown in FIG. 13, a liquid crystal displaydevice 1 of the present embodiment includes, in the following order fromthe viewing surface side, the first polarizer 1P, a viewing anglecompensation layer 30B, the first positive A plate 1A having an in-planeretardation of 120 nm or greater and 155 nm or smaller, the positive Cplate 1C having a thickness retardation of 80 nm or greater and 100 nmor smaller, the first substrate 100, the second positive A plate 2Ahaving an in-plane retardation of 120 nm or greater and 155 nm orsmaller, the horizontally aligned liquid crystal layer 1L, the secondsubstrate 200, and the second polarizer 2P. The viewing anglecompensation layer 30B is the biaxial retardation layer 32T1 having anin-plane retardation of 80 nm or greater and 100 nm or smaller and an NZcoefficient of 1.3 or greater and 1.5 or smaller. The device furtherincludes, between the viewing angle compensation layer 30B and the firstpositive A plate 1A, the biaxial retardation layer 13C having anin-plane retardation of 50 nm or greater and 70 nm or smaller and an NZcoefficient of −2.0 or greater and −1.6 or smaller.

The liquid crystal display device 1 of the present embodiment has thesame structure as the liquid crystal display device 1 of Embodiment 2-2except that the positive C plate 11C and the biaxial retardation layer32T2 in the liquid crystal display device 1 of Embodiment 2-2 areintegrated into the biaxial retardation layer 13C. In other words, theliquid crystal display device 1 of the present embodiment is opticallyequal to the liquid crystal display device 1 of Embodiment 2-2 and,similarly to Embodiment 2-2, can prevent deterioration in fragileness ofthe out-cell retardation layer 21, reflection of external light, andlight leakage when viewed from oblique directions in the black displaystate. The present embodiment, which employs a structure in which thepositive C plate 11C and the biaxial retardation layer 32T2 areintegrated, can eliminate an adhesive layer to reduce the thickness ofthe biaxial retardation layer 13C. The present embodiment, which reducesthe number of layers to be laminated and thereby reduces productionsteps, can also reduce the costs. An increase in the number of layers tobe laminated may reduce the yield because of contamination by foreignsubstances. Such a reduction in yield is avoidable by integrating thepositive C plate 11C and the biaxial retardation layer 32T2 and therebyreducing the number of layers laminated.

The biaxial retardation layer 13C preferably has an in-plane retardationof 52 nm or greater and 68 nm or smaller and an NZ coefficient of −1.95or greater and −1.65 or smaller, and more preferably has an in-planeretardation of 55 nm or greater and 65 nm or smaller and an NZcoefficient of −1.9 or greater and −1.7 or smaller.

The biaxial retardation layer 13C may be formed by the same method asfor the biaxial retardation layer 32T2.

Embodiment 5

In the present embodiment, the features unique to the present embodimentare mainly described and the same features as those in the aboveembodiment are not described again. The liquid crystal display device ofthe present embodiment has the same structure as the liquid crystaldisplay device 1 of Embodiment 2-3 except that the positive C plate 11Cand the biaxial retardation layer 33T2 are integrated into one layer(the later-described biaxial retardation layer 14C having an in-planeretardation of 10 nm or greater and 30 nm or smaller and an NZcoefficient of −7.5 or greater and −6.5 or smaller). The following isdescription in detail.

FIG. 14 is a schematic cross-sectional view of a liquid crystal displaydevice of Embodiment 5. As shown in FIG. 14, a liquid crystal displaydevice 1 of the present embodiment includes, in the following order fromthe viewing surface side, the first polarizer 1P, a viewing anglecompensation layer 30C, the first positive A plate 1A having an in-planeretardation of 120 nm or greater and 155 nm or smaller, the positive Cplate 1C having a thickness retardation of 80 nm or greater and 100 nmor smaller, the first substrate 100, the second positive A plate 2Ahaving an in-plane retardation of 120 nm or greater and 155 nm orsmaller, the horizontally aligned liquid crystal layer 1L, the secondsubstrate 200, and the second polarizer 2P. The viewing anglecompensation layer 30C is the biaxial retardation layer 33T1 having anin-plane retardation of 100 nm or greater and 130 nm or smaller and anNZ coefficient of 1.1 or greater and 1.3 or smaller. The device furtherincludes, between the viewing angle compensation layer 30C and the firstpositive A plate 1A, the biaxial retardation layer 14C having anin-plane retardation of 10 nm or greater and 30 nm or smaller and an NZcoefficient of −7.5 or greater and −6.5 or smaller.

The liquid crystal display device 1 of the present embodiment has thesame structure as the liquid crystal display device 1 of Embodiment 2-3except that the positive C plate 11C and the biaxial retardation layer33T2 in the liquid crystal display device 1 of Embodiment 2-3 areintegrated into the biaxial retardation layer 14C. In other words, theliquid crystal display device 1 of the present embodiment is opticallyequal to the liquid crystal display device 1 of Embodiment 2-3 and,similarly to Embodiment 2-3, can prevent deterioration in fragileness ofthe out-cell retardation layer 21, reflection of external light, andlight leakage when viewed from oblique directions in the black displaystate. The present embodiment, which employs a structure in which thepositive C plate 11C and the biaxial retardation layer 33T2 areintegrated, can eliminate an adhesive layer to reduce the thickness ofthe biaxial retardation layer 14C. The present embodiment, which reducesthe number of layers to be laminated and thereby reduces productionsteps, can also reduce the costs. An increase in the number of layers tobe laminated may reduce the yield because of contamination by foreignsubstances. Such a reduction in yield is avoidable by integrating thepositive C plate 11C and the biaxial retardation layer 33T2 and therebyreducing the number of layers laminated.

The biaxial retardation layer 14C preferably has an in-plane retardationof 12 nm or greater and 28 nm or smaller and an NZ coefficient of −7.4or greater and −6.6 or smaller, and more preferably has an in-planeretardation of 15 nm or greater and 25 nm or smaller and an NZcoefficient of −7.3 or greater and −6.7 or smaller.

The biaxial retardation layer 14C may be formed by the same method asfor the biaxial retardation layer 32T2.

The present invention is described below in more detail based onexamples and comparative examples. The examples, however, are notintended to limit the scope of the present invention.

Example 1

FIG. 15 is a schematic cross-sectional view of a liquid crystal displaydevice of Example 1. In Example 1, a liquid crystal display device 1having the same structure as in Embodiment 1-1 was discussed. In theschematic cross-sectional views of the examples and comparative examplesof the description, the “+A-Plate” means a positive A plate, the“+C-Plate” means a positive C plate, the “FFS-LC” means a FFS modeliquid crystal layer that is a horizontally aligned liquid crystallayer, the angles of the first and second polarizers indicate theazimuth angles of their absorption axes, the angle of the liquid crystallayer indicates the alignment azimuth of liquid crystal molecules in theblack display state, and the angles of the other layers indicate theazimuth angles of their slow axes.

In the liquid crystal display device 1 of Example 1, having thestructure as shown in FIG. 15, the transmittance viewing angle in theblack display state with light having a wavelength of 550 nm wassimulated at all the azimuths within the range of the polar angle of 0°to 80°, using a LCD-Master available from Shintec Co., Ltd. FIG. 16 is asimulation result of the transmittance viewing angle in the blackdisplay state of the liquid crystal display device of Example 1.

Example 2

FIG. 17 is a schematic cross-sectional view of a liquid crystal displaydevice of Example 2. In Example 2, the transmittance viewing angle inthe black display state was simulated for a liquid crystal displaydevice 1 having the same structure as in Embodiment 1-1 in the samemanner as in Example 1. FIG. 18 is a simulation result of thetransmittance viewing angle in the black display state of the liquidcrystal display device of Example 2.

Comparative Example 1

FIG. 39 is a schematic cross-sectional view of a liquid crystal displaydevice of Comparative Example 1. A liquid crystal display device 1R ofComparative Example 1 has the same structure as the liquid crystaldisplay devices 1 of Examples 1 and 2 except that the device does notinclude the out-cell retardation layer 21, the in-cell retardation layer22, and the positive C plate 11C. The transmittance viewing angle in theblack display state was simulated for the liquid crystal display device1R of Comparative Example 1 in the same manner as in Example 1. FIG. 40is a simulation result of the transmittance viewing angle in the blackdisplay state of the liquid crystal display device of ComparativeExample 1.

Comparative Example 2

FIG. 41 is a schematic cross-sectional view of a liquid crystal displaydevice of Comparative Example 2. A liquid crystal display device 1R ofComparative Example 2 has the same structure as the liquid crystaldisplay devices 1 of Examples 1 and 2 except that the device does notinclude the positive C plate 11C. The transmittance viewing angle in theblack display state was simulated for the liquid crystal display device1R of Comparative Example 2 in the same manner as in Example 1. FIG. 42is a simulation result of the transmittance viewing angle in the blackdisplay state of the liquid crystal display device of ComparativeExample 2.

(Comparison Between Examples 1 and 2 and Comparative Examples 1 and 2)

As shown in FIG. 40, the liquid crystal display device 1R of ComparativeExample 1 suppresses light leakage when viewed from oblique directionsto achieve a good contrast ratio viewing angle. Unfortunately, theliquid crystal display device 1R does not include an out-cellretardation layer and an in-cell retardation layer and thus cannotsuppress reflection of external light. In contrast, the liquid crystaldisplay device 1R of Comparative Example 2 includes the out-cellretardation layer 21 and the in-cell retardation layer 22 to suppressreflection of external light. Unfortunately, as shown in FIG. 42, thedevice causes a large amount of light leakage when viewed from obliquedirections (particularly around positions with a polar angle θ=60° andan azimuth angle ϕ=45°, 135°, 225°, or 315°) in the black display stateto reduce the contrast ratio viewing angle.

The liquid crystal display devices 1 of Examples 1 and 2, each of whichincludes the out-cell retardation layer 21 and the in-cell retardationlayer 22, can suppress reflection of external light and light leakagewhen viewed from oblique directions in the black display state as shownin FIG. 16 and FIG. 18. As described above, a typical horizontallyaligned liquid crystal display device including an out-cell retardationlayer and an in-cell retardation layer causes light leakage when viewedfrom oblique directions in the black display state to reduce the CRviewing angle in the black display state. Fortunately, the liquidcrystal display devices 1 of Examples 1 and 2 achieved a good contrastratio viewing angle like in the case of a horizontally aligned liquidcrystal display device (liquid crystal display device of ComparativeExample 1) without an out-cell retardation layer and an in-cellretardation layer. This is presumably an effect given by disposing thepositive C plate 11C in addition to the viewing angle compensation layer30.

Example 3

FIG. 19 is a schematic cross-sectional view of a liquid crystal displaydevice of Example 3. In Example 3, the transmittance viewing angle inthe black display state was simulated for a liquid crystal displaydevice 1 having the same structure as in Embodiment 2-1 in the samemanner as in Example 1. FIG. 20 is a simulation result of thetransmittance viewing angle in the black display state of the liquidcrystal display device of Example 3.

Example 4

FIG. 21 is a schematic cross-sectional view of a liquid crystal displaydevice of Example 4. In Example 4, the transmittance viewing angle inthe black display state was simulated for a liquid crystal displaydevice 1 having the same structure as in Embodiment 3 in the same manneras in Example 1. FIG. 22 is a simulation result of the transmittanceviewing angle in the black display state of the liquid crystal displaydevice of Example 4.

Example 5

FIG. 23 is a schematic cross-sectional view of a liquid crystal displaydevice of Example 5. In Example 5, the transmittance viewing angle inthe black display state was simulated for a liquid crystal displaydevice 1 having the same structure as in Embodiment 3 in the same manneras in Example 1. FIG. 24 is a simulation result of the transmittanceviewing angle in the black display state of the liquid crystal displaydevice of Example 5.

Comparative Example 3

FIG. 43 is a schematic cross-sectional view of a liquid crystal displaydevice of Comparative Example 3. A liquid crystal display device 1R ofComparative Example 3 has the same structure as the liquid crystaldisplay device 1 of Example 3 except that the device does not includethe out-cell retardation layer 21, the in-cell retardation layer 22, andthe positive C plate 11C. The transmittance viewing angle in the blackdisplay state was simulated for the liquid crystal display device 1R ofComparative Example 3 in the same manner as in Example 1. FIG. 44 is asimulation result of the transmittance viewing angle in the blackdisplay state of the liquid crystal display device of ComparativeExample 3.

Comparative Example 4

FIG. 45 is a schematic cross-sectional view of a liquid crystal displaydevice of Comparative Example 4. A liquid crystal display device 1R ofComparative Example 4 has the same structure as the liquid crystaldisplay device 1 of Example 3 except that the device does not includethe positive C plate 11C. The transmittance viewing angle in the blackdisplay state was simulated for the liquid crystal display device 1R ofComparative Example 4 in the same manner as in Example 1. FIG. 46 is asimulation result of the transmittance viewing angle in the blackdisplay state of the liquid crystal display device of ComparativeExample 4.

(Comparison Between Examples 3 to 5 and Comparative Examples 3 and 4)

As shown in FIG. 44, the liquid crystal display device 1R of ComparativeExample 3 suppresses light leakage when viewed from oblique directionsto achieve a good contrast ratio viewing angle. Unfortunately, theliquid crystal display device 1R does not include an out-cellretardation layer and an in-cell retardation layer and thus cannotsuppress reflection of external light. In contrast, the liquid crystaldisplay device 1R of Comparative Example 4 includes the out-cellretardation layer 21 and the in-cell retardation layer 22 to suppressreflection of external light. Unfortunately, as shown in FIG. 46, thedevice causes a large amount of light leakage when viewed from obliquedirections (particularly around positions with a polar angle θ=60° andan azimuth angle ϕ=45°, 135°, 225°, or 315°) in the black display stateto reduce the contrast ratio viewing angle.

The liquid crystal display devices 1 of Examples 3 to 5, each of whichincludes the out-cell retardation layer 21 and the in-cell retardationlayer 22, can suppress reflection of external light and light leakagewhen viewed from oblique directions in the black display state as shownin FIG. 20, FIG. 22, and FIG. 24. As described above, a typicalhorizontally aligned liquid crystal display device including an out-cellretardation layer and an in-cell retardation layer causes light leakagewhen viewed from oblique directions in the black display state to reducethe CR viewing angle in the black display state. Fortunately, the liquidcrystal display devices 1 of Examples 3 to 5 achieved a good contrastratio viewing angle like in the case of a horizontally aligned liquidcrystal display device (liquid crystal display device of ComparativeExample 3) without an out-cell retardation layer and an in-cellretardation layer. This is presumably an effect given by disposing thepositive C plate 11C in addition to the viewing angle compensation layer30. Example 3 employs the positive C plate 11C disposed separately fromthe viewing angle compensation layer 30. Example 4 employs the positiveC plate 12C in which the positive C plate 31C included in the viewingangle compensation layer 30 of Example 3 and the positive C plate 11Care integrated. These examples show that light leakage when viewed fromoblique directions in the black display state can be suppressed both inthe case of disposing the positive C plate 11C separately from theviewing angle compensation layer 30 and in the case of disposing thepositive C plate 11C integrated with a layer of the viewing anglecompensation layer 30.

Example 6

FIG. 25 is a schematic cross-sectional view of a liquid crystal displaydevice of Example 6. In Example 6, the transmittance viewing angle inthe black display state was simulated for a liquid crystal displaydevice 1 having the same structure as in Embodiment 2-2 in the samemanner as in Example 1. FIG. 26 is a simulation result of thetransmittance viewing angle in the black display state of the liquidcrystal display device of Example 6.

Example 7

FIG. 27 is a schematic cross-sectional view of a liquid crystal displaydevice of Example 7. In Example 7, the transmittance viewing angle inthe black display state was simulated for a liquid crystal displaydevice 1 having the same structure as in Embodiment 4 in the same manneras in Example 1. FIG. 28 is a simulation result of the transmittanceviewing angle in the black display state of the liquid crystal displaydevice of Example 7.

Comparative Example 5

FIG. 47 is a schematic cross-sectional view of a liquid crystal displaydevice of Comparative Example 5. A liquid crystal display device 1R ofComparative Example 5 has the same structure as the liquid crystaldisplay device 1 of Example 6 except that the device does not includethe out-cell retardation layer 21, the in-cell retardation layer 22, andthe positive C plate 11C. The transmittance viewing angle in the blackdisplay state was simulated for the liquid crystal display device 1R ofComparative Example 5 in the same manner as in Example 1. FIG. 48 is asimulation result of the transmittance viewing angle in the blackdisplay state of the liquid crystal display device of ComparativeExample 5.

Comparative Example 6

FIG. 49 is a schematic cross-sectional view of a liquid crystal displaydevice of Comparative Example 6. A liquid crystal display device 1R ofComparative Example 6 has the same structure as the liquid crystaldisplay device 1 of Example 6 except that the device does not includethe positive C plate 11C. The transmittance viewing angle in the blackdisplay state was simulated for the liquid crystal display device 1R ofComparative Example 6 in the same manner as in Example 1. FIG. 50 is asimulation result of the transmittance viewing angle in the blackdisplay state of the liquid crystal display device of ComparativeExample 6.

(Comparison Between Examples 6 and 7 and Comparative Examples 5 and 6)

As shown in FIG. 48, the liquid crystal display device 1R of ComparativeExample 5 suppresses light leakage when viewed from oblique directionsto achieve a good contrast ratio viewing angle. Unfortunately, theliquid crystal display device 1R does not include an out-cellretardation layer and an in-cell retardation layer and thus cannotsuppress reflection of external light. In contrast, the liquid crystaldisplay device 1R of Comparative Example 6 includes the out-cellretardation layer 21 and the in-cell retardation layer 22 to suppressreflection of external light. Unfortunately, as shown in FIG. 50, thedevice causes a large amount of light leakage when viewed from obliquedirections (particularly around positions with a polar angle θ=60° andan azimuth angle ϕ=45°, 135°, 225°, or 315°) in the black display stateto reduce the contrast ratio viewing angle.

The liquid crystal display devices 1 of Examples 6 and 7, each of whichincludes the out-cell retardation layer 21 and the in-cell retardationlayer 22, can suppress reflection of external light and light leakagewhen viewed from oblique directions in the black display state as shownin FIG. 26 and FIG. 28. As described above, a typical horizontallyaligned liquid crystal display device including an out-cell retardationlayer and an in-cell retardation layer causes light leakage when viewedfrom oblique directions in the black display state to reduce the CRviewing angle in the black display state. Fortunately, the liquidcrystal display devices 1 of Examples 6 and 7 achieved a good contrastratio viewing angle like in the case of a horizontally aligned liquidcrystal display device (liquid crystal display device of ComparativeExample 5) without an out-cell retardation layer and an in-cellretardation layer. This is presumably an effect given by disposing thepositive C plate 11C in addition to the viewing angle compensation layer30. Example 6 employs the positive C plate 11C disposed separately fromthe viewing angle compensation layer 30. Example 7 employs the biaxialretardation layer 13C in which the biaxial retardation layer 32 includedin the viewing angle compensation layer 30 of Example 6 and the positiveC plate 11C are integrated. These examples show that light leakage whenviewed from oblique directions in the black display state can besuppressed both in the case of disposing the positive C plate 11Cseparately from the viewing angle compensation layer 30 and in the caseof disposing the positive C plate 11C integrated with a layer of theviewing angle compensation layer 30.

Although Examples 1 to 19 employ different kinds of viewing anglecompensation layers 30 with different structures (first laminate 31,second laminate 32, third laminate 33, and λ/2 plate 301), all theviewing angle compensation layers 30 have the same function (thefunction of converting linearly polarized light having passed throughthe second polarizer 2P into linearly polarized light parallel to theabsorption axis of the first polarizer 1P) and thus are optically equalto one another as a whole. Accordingly, a liquid crystal display device,in which the viewing angle compensation layer 30 in the liquid crystaldisplay device 1 of Example 1 is replaced by the viewing anglecompensation layer 30 used in Example 6 such that the biaxialretardation layer 32T1 and the biaxial retardation layer 32T2 aredisposed in the given order from the second polarizer 2P side, can alsosuppress reflection of external light and light leakage when viewed fromoblique directions in the black display state.

Example 8

FIG. 29 is a schematic cross-sectional view of a liquid crystal displaydevice of Example 8. In Example 8, the transmittance viewing angle inthe black display state was simulated for a liquid crystal displaydevice 1 having the same structure as in Embodiment 2-3 in the samemanner as in Example 1. FIG. 30 is a simulation result of thetransmittance viewing angle in the black display state of the liquidcrystal display device of Example 8.

Example 9

FIG. 31 is a schematic cross-sectional view of a liquid crystal displaydevice of Example 9. In Example 9, the transmittance viewing angle inthe black display state was simulated for a liquid crystal displaydevice 1 having the same structure as in Embodiment 5 in the same manneras in Example 1. FIG. 32 is a simulation result of the transmittanceviewing angle in the black display state of the liquid crystal displaydevice of Example 9.

Comparative Example 7

FIG. 51 is a schematic cross-sectional view of a liquid crystal displaydevice of Comparative Example 7. A liquid crystal display device 1R ofComparative Example 7 has the same structure as the liquid crystaldisplay device 1 of Example 8 except that the device does not includethe out-cell retardation layer 21, the in-cell retardation layer 22, andthe positive C plate 11C. The transmittance viewing angle in the blackdisplay state was simulated for the liquid crystal display device 1R ofComparative Example 7 in the same manner as in Example 1. FIG. 52 is asimulation result of the transmittance viewing angle in the blackdisplay state of the liquid crystal display device of ComparativeExample 7.

Comparative Example 8

FIG. 53 is a schematic cross-sectional view of a liquid crystal displaydevice of Comparative Example 8. A liquid crystal display device 1R ofComparative Example 8 has the same structure as the liquid crystaldisplay device 1 of Example 8 except that the device does not includethe positive C plate 11C. The transmittance viewing angle in the blackdisplay state was simulated for the liquid crystal display device 1R ofComparative Example 8 in the same manner as in Example 1. FIG. 54 is asimulation result of the transmittance viewing angle in the blackdisplay state of the liquid crystal display device of ComparativeExample 8.

(Comparison Between Examples 8 and 9 and Comparative Examples 7 and 8)

As shown in FIG. 52, the liquid crystal display device 1R of ComparativeExample 7 suppresses light leakage when viewed from oblique directionsto achieve a good contrast ratio viewing angle. Unfortunately, theliquid crystal display device 1R does not include an out-cellretardation layer and an in-cell retardation layer and thus cannotsuppress reflection of external light. In contrast, the liquid crystaldisplay device 1R of Comparative Example 8 includes the out-cellretardation layer 21 and the in-cell retardation layer 22 to suppressreflection of external light. Unfortunately, as shown in FIG. 54, thedevice causes a large amount of light leakage when viewed from obliquedirections (particularly around positions with a polar angle θ=60° andan azimuth angle ϕ=45°, 135°, 225°, or 315°) in the black display stateto reduce the contrast ratio viewing angle.

The liquid crystal display devices 1 of Examples 8 and 9, each of whichincludes the out-cell retardation layer 21 and the in-cell retardationlayer 22, can suppress reflection of external light and light leakagewhen viewed from oblique directions in the black display state as shownin FIG. 30 and FIG. 32. As described above, a typical horizontallyaligned liquid crystal display device including an out-cell retardationlayer and an in-cell retardation layer causes light leakage when viewedfrom oblique directions in the black display state to reduce the CRviewing angle in the black display state. Fortunately, the liquidcrystal display devices 1 of Examples 8 and 9 achieved a good contrastratio viewing angle like in the case of a horizontally aligned liquidcrystal display device (liquid crystal display device of ComparativeExample 7) without an out-cell retardation layer and an in-cellretardation layer. This is presumably an effect given by disposing thepositive C plate 11C in addition to the viewing angle compensation layer30. Example 8 employs the positive C plate 11C disposed separately fromthe viewing angle compensation layer 30. Example 9 employs the biaxialretardation layer 14C in which the biaxial retardation layer 33T2included in the viewing angle compensation layer 30 of Example 8 and thepositive C plate 11C are integrated. These examples show that lightleakage when viewed from oblique directions in the black display statecan be suppressed both in the case of disposing the positive C plate 11Cseparately from the viewing angle compensation layer 30 and in the caseof disposing the positive C plate 11C integrated with a layer of theviewing angle compensation layer 30.

Although Examples 1 to 19 employ different kinds of viewing anglecompensation layers 30 with different structures (first laminate 31,second laminate 32, third laminate 33, and λ/2 plate 301), all of theviewing angle compensation layers 30 are optically equal to one anotheras a whole, as described above. Accordingly, a liquid crystal displaydevice, in which the viewing angle compensation layer 30 in the liquidcrystal display device 1 of Example 1 is replaced by the viewing anglecompensation layer 30 used in Example 8 such that the biaxialretardation layer 33T1 and the biaxial retardation layer 33T2 aredisposed in the given order from the second polarizer 2P side, can alsosuppress reflection of external light and light leakage when viewed fromoblique directions in the black display state.

Example 10

FIG. 33 is a schematic cross-sectional view of a liquid crystal displaydevice of Example 10. In Example 10, the transmittance viewing angle inthe black display state was simulated for a liquid crystal displaydevice 1 having the same structure as in Embodiment 2-4 in the samemanner as in Example 1. FIG. 34 is a simulation result of thetransmittance viewing angle in the black display state of the liquidcrystal display device of Example 10.

Comparative Example 9

FIG. 55 is a schematic cross-sectional view of a liquid crystal displaydevice of Comparative Example 9. A liquid crystal display device 1R ofComparative Example 9 has the same structure as the liquid crystaldisplay device 1 of Example 10 except that the device does not includethe out-cell retardation layer 21, the in-cell retardation layer 22, andthe positive C plate 11C. The transmittance viewing angle in the blackdisplay state was simulated for the liquid crystal display device 1R ofComparative Example 9 in the same manner as in Example 1. FIG. 56 is asimulation result of the transmittance viewing angle in the blackdisplay state of the liquid crystal display device of ComparativeExample 9.

Comparative Example 10

FIG. 57 is a schematic cross-sectional view of a liquid crystal displaydevice of Comparative Example 10. A liquid crystal display device 1R ofComparative Example 10 has the same structure as the liquid crystaldisplay device 1 of Example 10 except that the device does not includethe positive C plate 11C. The transmittance viewing angle in the blackdisplay state was simulated for the liquid crystal display device 1R ofComparative Example 10 in the same manner as in Example 1. FIG. 58 is asimulation result of the transmittance viewing angle in the blackdisplay state of the liquid crystal display device of ComparativeExample 10.

(Comparison Between Example 10 and Comparative Examples 9 and 10)

As shown in FIG. 56, the liquid crystal display device 1R of ComparativeExample 9 suppresses light leakage when viewed from oblique directionsto achieve a good contrast ratio viewing angle. Unfortunately, theliquid crystal display device 1R does not include an out-cellretardation layer and an in-cell retardation layer and thus cannotsuppress reflection of external light. In contrast, the liquid crystaldisplay device 1R of Comparative Example 10 includes the out-cellretardation layer 21 and the in-cell retardation layer 22 to suppressreflection of external light. Unfortunately, as shown in FIG. 58, thedevice causes a large amount of light leakage when viewed from obliquedirections (particularly around positions with a polar angle θ=60° andan azimuth angle ϕ=45°, 135°, 225°, or 315°) in the black display stateto reduce the contrast ratio viewing angle.

The liquid crystal display device 1 of Example 10, which includes theout-cell retardation layer 21 and the in-cell retardation layer 22, cansuppress reflection of external light and light leakage when viewed fromoblique directions in the black display state as shown in FIG. 34. Asdescribed above, a typical horizontally aligned liquid crystal displaydevice including an out-cell retardation layer and an in-cellretardation layer causes light leakage when viewed from obliquedirections in the black display state to reduce the CR viewing angle inthe black display state. Fortunately, the liquid crystal display device1 of Example 10 achieved a good contrast ratio viewing angle like in thecase of a horizontally aligned liquid crystal display device (liquidcrystal display device of Comparative Example 9) without an out-cellretardation layer and an in-cell retardation layer. This is presumablyan effect given by disposing the positive C plate 11C in addition to theviewing angle compensation layer 30.

Although Examples 1 to 19 employ different kinds of viewing anglecompensation layers 30 with different structures (first laminate 31,second laminate 32, third laminate 33, and λ/2 plate 301), all of theviewing angle compensation layers 30 are optically equal to one anotheras a whole, as described above. Accordingly, a liquid crystal displaydevice, in which the viewing angle compensation layer 30 in the liquidcrystal display device 1 of Example 1 is replaced by the viewing anglecompensation layer 30 used in Example 10, which is the λ/2 plate 301,can also suppress reflection of external light and light leakage whenviewed from oblique directions in the black display state.

Examples 11 to 14 and Comparative Examples 11 and 12

In each of Examples 11 to 14 and Comparative Examples 11 and 12, thethickness retardation of the positive C plate 11C employed in Example 1was changed to the value shown in Table 1. Then, the averagetransmittance value at the polar angle θ=60° was calculated. The averagetransmittance value is the average of transmittance values in the blackdisplay state determined for every 5° in the range of the azimuth angleof 0° to 360°. The transmittance value at each azimuth angle wasdetermined by simulation using a LCD-Master available from Shintec Co.,Ltd. The average transmittance value was also determined for Examples 1and 2 and Comparative Example 2 in the same manner as in Examples 11 to14 and Comparative Examples 11 and 12. Table 1 shows the results.

TABLE 1 Com- Com- Com- parative parative parative Example 2 Example 11Example 11 Example 12 Example 13 Example 1 Example 2 Example 14 Example12 Thickness — 20 30 40 50 60 70 80 90 retardation (Rth) of positive Cplate between first polarizer and first positive A plate Average 0.00310.0014 0.0008 0.0004 0.0002 0.0001 0.0003 0.0006 0.0011 transmittancevalue

(Evaluation of Examples 1, 2, and 11 to 14, and Comparative Examples 2,11, and 12)

Table 1 shows that the average transmittance value in the black displaystate can be reduced to 0.0010 or lower by setting the thicknessretardation of the positive C plate 11C disposed between the firstpolarizer 1P and the first positive A plate 1A to 30 nm or greater and80 nm or smaller.

Examples 15 to 19 and Comparative Examples 13 and 14

In each of Examples 15 to 19 and Comparative Examples 13 and 14, thethickness retardation of the positive C plate 11C employed in Example 3was changed to the value shown in Table 2. Then, the averagetransmittance value at the polar angle θ=60° was calculated in the samemanner as in Examples 11 to 14 and Comparative Examples 11 and 12. Theaverage transmittance value was also determined for Example 3 andComparative Example 4 in the same manner as in Examples 11 to 14 andComparative Examples 11 and 12. Table 2 shows the results.

TABLE 2 Com- Com- Com- parative parative Example Example Example ExampleExample Example parative Example 4 Example 13 15 16 3 17 18 19 Example14 Thickness — 20 30 40 50 60 70 80 90 retardation (Rth) of positive Cplate between viewing angle compensation layer and first positive Aplate Average 0.0022 0.0008 0.0004 0.0001 0.0001 0.0002 0.0005 0.00100.0017 transmittance value

(Evaluation of Examples 3 and 15 to 19 and Comparative Examples 4, 13,and 14)

Table 2 shows that the average transmittance value in the black displaystate can be reduced to 0.0010 or lower by setting the thicknessretardation of the positive C plate 11C disposed between the viewingangle compensation layer 30 and the first positive A plate 1A to 30 nmor greater and 80 nm or smaller.

As shown in Examples 1 to 3 and 11 to 19 in Table 1 and Table 2, theaverage transmittance value can be reduced to a half or lower of that inComparative Example 4 by setting the thickness retardation of thepositive C plate 11C disposed between the first polarizer 1P and thefirst positive A plate 1A or between the viewing angle compensationlayer 30 and the first positive A plate 1A to 30 nm or greater and 80 nmor smaller. A positive C plate 11C having a thickness retardation ofsmaller than 30 nm or greater than 80 nm increases the averagetransmittance value and reduces the viewing angle, thereby reducing themerit of disposing the positive C plate 11C between the first polarizer1P and the first positive A plate 1A or between the viewing anglecompensation layer 30 and the first positive A plate 1A.

What is claimed is:
 1. A liquid crystal display device comprising in thefollowing order from a viewing surface side: a first polarizer; aviewing angle compensation layer; a first positive A plate having anin-plane retardation of 120 nm or greater and 155 nm or smaller; apositive C plate having a thickness retardation of 80 nm or greater and100 nm or smaller; a first substrate; a second positive A plate havingan in-plane retardation of 120 nm or greater and 155 nm or smaller; ahorizontally aligned liquid crystal layer; a second substrate; and asecond polarizer, the liquid crystal display device further comprisingbetween the viewing angle compensation layer and the first positive Aplate a positive C plate having a thickness retardation of 30 nm orgreater and 80 nm or smaller.
 2. The liquid crystal display deviceaccording to claim 1, wherein the viewing angle compensation layer is alaminate including in the following order from a first polarizer side apositive A plate having an in-plane retardation of 130 nm or greater and150 nm or smaller and a positive C plate having a thickness retardationof 80 nm or greater and 100 nm or smaller.
 3. The liquid crystal displaydevice according to claim 1, wherein the viewing angle compensationlayer is a laminate including in the following order from a firstpolarizer side a biaxial retardation layer having an in-planeretardation of 80 nm or greater and 100 nm or smaller and an NZcoefficient of 1.3 or greater and 1.5 or smaller and a biaxialretardation layer having an in-plane retardation of 50 nm or greater and70 nm or smaller and an NZ coefficient of −1.2 or greater and −0.8 orsmaller.
 4. The liquid crystal display device according to claim 1,wherein the viewing angle compensation layer is a laminate including inthe following order from a first polarizer side a biaxial retardationlayer having an in-plane retardation of 100 nm or greater and 130 nm orsmaller and an NZ coefficient of 1.1 or greater and 1.3 or smaller and abiaxial retardation layer having an in-plane retardation of 10 nm orgreater and 30 nm or smaller and an NZ coefficient of −4.5 or greaterand −3.5 or smaller.
 5. The liquid crystal display device according toclaim 1, wherein the viewing angle compensation layer is a λ/2 platehaving an in-plane retardation of 230 nm or greater and 320 nm orsmaller and an NZ coefficient of 0.4 or greater and 0.6 or smaller.
 6. Aliquid crystal display device comprising in the following order from aviewing surface side: a first polarizer; a viewing angle compensationlayer; a first positive A plate having an in-plane retardation of 120 nmor greater and 155 nm or smaller; a positive C plate having a thicknessretardation of 80 nm or greater and 100 nm or smaller; a firstsubstrate; a second positive A plate having an in-plane retardation of120 nm or greater and 155 nm or smaller; a horizontally aligned liquidcrystal layer; a second substrate; and a second polarizer, the viewingangle compensation layer being a biaxial retardation layer having anin-plane retardation of 100 nm or greater and 130 nm or smaller and anNZ coefficient of 1.1 or greater and 1.3 or smaller, the liquid crystaldisplay device further comprising between the viewing angle compensationlayer and the first positive A plate a biaxial retardation layer havingan in-plane retardation of 10 nm or greater and 30 nm or smaller and anNZ coefficient of −7.5 or greater and −6.5 or smaller.